I was wondering how hard/cost wise would it be to change a regular tremelo to a floyd rose? Or, would it be cheaper to buy a new guitar with a floyd rose already installed?
Depends what kind of guitar you have.
it would be easier to buy a guitar with a floyd in it. An origional FR is about £140. Fitting requires extra routing etc. Perhaps a pro could do it for you.
it's simple. you just need a router
Your best bet is to take your guitar to a music store and ask the guitar tech how much.