Buy Stuff
First, buy some recessed lights. Then buy a another set of recessed lights. Let's worry about returning stuff later. Also, buy as many circuits and switches as you please. You can never have too many. Oh, and buy a tub.
Stick New Stuff To Old Stuff
Take all your new stuff and nail, screw, glue or otherwise make it stick to the existing old stuff (wall studs, ceiling frame, pipes). Word of warning: if you use something called Great Stuff either wear rubber gloves or be prepared to spend a lot of time scraping your hands until you see the dermis.
