What UV filter brand is best for Nikon D90?

I would like to invest into a lense protector for my Nikkor lense.mainly to just protect the lense from finger prints, scratches, and dust.
Are there any crappy, cheap filters out there, like Rocketfish? And on that note, should I purchase a UV filter or a "circular polarizer?" i really don't know.
i've heard that UV filters can cause mildew and fungus to grow on lense bcuz UV filter blocks sun? I mostly do urban photography and only take it to high altitude mountain trips for summer vacations. I have a 52 mm diameter lense i'm pretty sure, its the 0 with a slash across it right?
and how do you actually put on these filters? Is there enough room for the cap to go over it without scratching it [filter]? Sorry, a lotta question but i don't wanna screw this up. 10 points for best answer!

You have to choose the UV filter for the lens itself. One brand I trust is Hoya both my dad and I have them on all our lenses and they work perfectly. You will probably have to order them in though.

The one on my 18-55mm lens is the Hoya 52mm HMC UV(O).

as for worrying about putting the lens cap on, don't. The filter is just a tiny extension to your lens and the cap will fit into the filter like it does onto your lens now.

The filter will be a screw in filter, where you just screw it on

Another option would of course be to use the lkens hood and to actually take care of your gear.

Hoya, B+W, Nikon or Canon. A good multicoated filter. If it's cheaper than $15 then avoid.

The one about the mildew is a new one for me, nice for the fable collection