I'm currently getting to grips with my new NEX 3,..and I'm using Canon FD lenses rather than Nikon. However, I can say that you are probably going to be able to focus ok with a little familiarisation. I have the lower 'soft button B' customised for 'MF assist'. a single push gets a 7x rectangle that can be easily moved about the frame by the 4-way. A second push ups the mag to 14x. The screen reflects whatever is behind it thus preventing you from seeing clearly when the reflections are very bright. The answer is to make sure that you look into a dark reflection,..there are many and diverse ways of doing so from wearing a dark shirt to a small black card enclosure that apes the hoods on studio TV cameras etc....
....The real answer to this is to use the 'clearview' adaptation that is now widely shown on the web and is here on this site in the item about the new NEX C3. This allows one to use the lcd as an eye-level v/f so your face will exclude any bright reflections on the screen.