“Don’t do it.
Keep the cash for your own upgrade.”
^^^ This.
Plus, if you want it done by spring, you have already waited too long. The contractors you want are already booked, you will pay too much if you can find someone, or you will get very poor work.
This. I'm in the trades, and everyone [good] is backed up for months.
There are a lot of good posts upthread.
When I re-did my bathroom, I crafted it specifically for The Queen.
A house purchaser will likely have different ideas about redoing your [I presume] main bathroom. Unless you're a really good interior renovation designer, let it be.
The part about pre-buying the items is as ClearCase_guy wrote - they may not work.
See my comment about "really good interior renovation designer".