So this is a post in response to some questions I got from @jass: but rather than wall her I thought maybe I'd just post my info here so others could share their stories too!

Our situation, briefly:

LO used to be a great sleeper, then she got progressively worse until last week when she refused to sleep on her own at all. The first night I sat up all night rocking her and my husband stayed home from work so I could sleep. The 2nd and 3rd nights I sat up until 4am then gave up and coslept with her (which makes me extremely nervous and uncomfortable) out of desperation because I was afraid I'd fall asleep and drop her if I kept sitting up with her. That day we had her 6 mo checkup and the doc told me to sleep train the baby or stop driving because I was becoming a hazard to myself and others with my sleep deprivation. i didn't want to start that night because she wasn't feeling well after shots, and I was too tired to sit up with her, so we coslept that night too.

Saturday night we started sleeping training and it went like this:
8:07 put her down with a pacifier, a second pacifier by her hand, and a paci plushie (a wubbanub that you can use with any paci) for her to cuddle with. She kicked around grunting but not crying for a while.
8:20 start crying
8:25 went up for first check, gave her paci, stroked her head and told her I loved her but she needed to go to sleep now, left the room. She then just sort of kicked around for a while
8:50 started really pissed off crying
8:55 started over with check 1 bc it had been so long. went up for first (second) check, gave her paci, stroked her head and told her I loved her but she needed to go to sleep now, left the room.
9:05 went up for next check, gave her paci, stroked her head and told her I loved her but she needed to go to sleep now, left the room.
9:20 went up for next check and she had thrown up a little (not a ton, and it wasn't on her clothes just on her cheek/behind her head). I wiped her down and moved her so she wasn't near it in the crib. gave her paci, stroked her head and told her I loved her but she needed to go to sleep now, left the room.
9:20-9:59 she mostly screamed really hard and I mostly questioned my sanity. We went up 2 more times. It really sucked. I hated life and myself and stupid stupid sleeping training.
10:00 - HOLY SHIT SHE FELL ASLEEP.
10:45 - up and crying.
10:50 - went up for first check, gave her paci, stroked her head and told her I loved her but she needed to go to sleep now, left the room. She fell asleep right after
11:45 - up and crying
11:50 - went up for first check, gave her paci, stroked her head and told her I loved her but she needed to go to sleep now, left the room. Fell right back asleep
2:30- up and crying, but only for 4 minutes and fell back asleep on her own!!
4:30 - up and crying but only for 3 min and fell asleep on her own!
6am - up for the day, not crying just happily kicking around. this was her normal wake time. she did not appear traumatized, horse (I really thought she would be), nor did she appear to hate me at all. Huzzah! Babies are better people than parents are, truly.

Night 2:
8:15 - set her down
8:30 - start crying
8:35 - went up for first check, gave her paci, stroked her head and told her I loved her but she needed to go to sleep now, left the room. Then she just kicked around without crying for a bit
8:50- flipped to her stomach (which she hates) and started crying
8:58 - stopped crying on her own but not asleep and still on her stomach.
8:58-9:10 - She kept crying for like 30 seconds then calming like she was trying to go to sleep. I wasn't sure if I should go up or not since she was still crying on and off, but it seemed like she was winding down. But since it went on for that long I decided to go up and flip her back to her back and give her her paci back. When I got up there she'd thrown up a little again (or maybe just a lot of spit up? she is a reflux baby) but it wasn't on her clothes. I think she wanted to sleep but couldn't bc the sheet was wet under her, poor baby! I flipped her over, wiped her face, moved her down in the crib, gave her her paci, told her I loved her, and left.
9:15- rolled onto her side and fell asleep!!!!!!!!!!!!
11:45- awake and crying
11:49 - stopped crying and fell back asleep on her own
4:30 - awake and crying
4:32 - stopped crying and fell right back asleep on her own
6:25 - awake for the day, 30 min later than usual!!!!!!!!! Once again she was fine and no hard feelings

So I know we are only 2 nights in and we may still have some bumps in the road or regressions but my main feeling at this point is HOLY SHIT THIS WORKS. And I'm obviously pretty excited about it. I slept in my bed last night, with my husband, without getting out of bed even once for the baby, until 6:30am. That has not happened in MONTHS.

We are not nap training yet because we want to make sure she is well rested at bedtime each night and not overtired. After she seems really well established with night training (1-2 weeks?) we will nap train.

@jass: I hope I answered your questions but if not let me know!

Eta: we swaddle weaned into the Merlin suit 1 mo before this, and night 1 of Ferber was also her first night in a sleep sack. So it was sort of a double whammy sleep training and Merlin weaning at once (but she just about figured out how to roll in Merlin so it was necessary). Also shoutout to @blackbird: and @jojogirl: who harassed me into sleep training and answered my 475 questions and talked to me the whole worst-2-hrs-ever!!!!!!!!!!!!