What does 'redoing' a bathroom mean? For me that usually involves ripping it back to the framing...
If you just want to pain them it's the normal stuff with paint:
It's a bathroom, so the existing paint is probably high gloss, you want to score the entire surface with steel wool/sandpaper. Depending on how glossy and hard the existing paint is you may be able to skip this step.
Then you want to wash walls. There is a chemical for doing this, I'm not sure if Lowes or anyplace carries it, called TSP (Tri sodium phosphate) or something similar.
Mask off what you dont want to get paint on.
Primer is a necessity for a good 100% job. Primer has to match the finish paint whatever it may be, i.e. oil primer with oil paint etc. Reading the back of the paint cans comes in handy here.
The paint, it all depends on where you buy it. I dont know much about home depot because I honestly dont shop there. Usually someone can direct you in the correct direction in the store. I usually go to ICI Paints around simply because it's cheaper to buy in 20 gal buckets when you are repainting an entire floor... Whatever you get, if you apply it correctly and keep the bathroom ventilated it should hold up.
Applying is the 2nd most important part, after prep
You have to go carefully, but not so slow it dries. You have to apply just enough to cover the surface with each coat. You CANNOT put on a second coat until the first one is completely dry. You CANNOT use the bathroom at all until it is all done and the paint is completely dry.
I'd have tile installed, floor to ceiling, personally.