You certainly can 'skim coat' the vermiculite. Depending on how well you can use a trowel, it is something that you can DIY. If you decide to go this route, let me know and I'll give you a few pointers on mixing and applying the vermiculite. Also be sure to take the patched floor into account when measuring for the new liner, you don't want to fix the bottom only to cause wrinkles in the new liner!
I'm here almost every day, if you'd like a little more info or detail, just ask and I'll get back to you