Hey, I used to play keyboard some years ago. Nowadays I don't play it very much. I learned bass alone with the theory base that I had from the keyboard/piano classes, then I just needed to practice.
I accept requests of specific bass tabs, as long the song is not too boring and not too dificult for me. But I can make easy basslines for difficult songs too.
Also I have a channel on youtube with some bass covers, check it out if you don't have anything better to do =]: http://www.youtube.com/user/Gustavoveg02
and my email is: firstname.lastname@example.org