Many people (myself included) have successfuly finished guitars with Minwax Wipe-On Poly, Tru-Oil, and Watco Danish Oil, all of which should be available at Lowe's. They each have their advantages and disadvantages. A search in the DIY finishing forum will give you tons of info, as well as examples of each finish. Keep in mind, though, that while any of these should give you a nice smooth finish on the maple neck, they won't fill the pores of the ash body (not without 30~40 layers or something). This is OK if you want to feel the texture of the pores after the finish is applied, but you will have to use grain filler to get a nice level finish. Again, there is a ton of info on grain filling in the DIY finishing section. Good luck with your project!