As someone who can probably count on one hand how many full nights sleep they've had in 2.5 years, I understand how scary and tentative you're feeling right now.
I dont know of your dd's sleep history but my dd1 was about 18 months old before she felt comfortable enough to go to sleep on her own and dd2 seems to be following suit. Its our routine to cuddle our girls to sleep both day and night and yes I wondered how on earth I was going to be able to do this with dd1 after dd2 arrived. Obviously I could only hold one comfortably in my arms.
After having dd2 though, it started a new transition for dd1. If her day time nap co-incided with feeding dd2, then dd1 would just lie on the couch beside me and hold my hand while I was feeding dd2, and she would eventually just drift off to sleep. I could then put dd2 down and take dd1 off to bed. This transition then enabled her to feel confident enough to go to bed on her own.
Whilst many will think this should have been something that dd1 should have been able to do from only a few months old, it honestly broke my heart that she didnt need my arms wrapped around her anymore, to drift off to sleep.
DD1 also used to be up half the night until around 14 months. She would wake at around 1am and then be so wired from having a good 4 oor 5 hours sleep, that she wouldnt go back to sleep until about 4 or 5am.
Being heavily pregnant and boarderline immobile cause of SPD and looking after a 14 month old who was up half the night really made me question my sanity and why we'd go back for a second child.
But...like I said in my pp, you just adapt because you have to. Just remember to go with the flow and know that some days will be shear hell and some days will make you wonder how easy its been.
You will be fine!