Typically, flooring is installed with Tongue and Groove joints. This permits edge nailing of the trailing edge, while the leading edge slips into the trailing edge of the piece next to it. This allows completely hidden nailing. With a lap joint, you have to have nails on the trailing edge that are SURFACE nailed, and this IS NOT DESIRABLE!
There are hammer driven flooring nail guns on the market, and you should be able to rent them from most rental stores.
As far as finishes, Henry is our resident finish expert, so I'll leave that part to him. Henry?
Good luck on your project, I hope you haven't already purchased your materials...