There is an entire Sub-Forum dedicated to reapiring & replacing the floor (I've relocated this thread into it). You will find lots of experiences from mebers who have gone there before you! Browse around and feel free to post specific questions or problems as they arrive.
As far as replacing rivets, drill out the old ones with a bit the same size as the shank of the existing rivet. Then put the new rivet in the same hole using a rivet tool, here's a thread
that talks about it more in-depth, I think it's mostly on exterior rivets, but the process & tools are the same.
Oh yeah, welcome to the forums!