Any keyboard/piano player out there?

I've played keyboard for my church for almost three years. I got up to Grade 7 in Royal Conservatory of Music and completed Grade 1 Theory before i had to quit to go to unviersity. We're given only chords at church to play the music (it's a band thing with drums, guitars etc). I've been ad libbin most of the time. I think I'm alright. But I have a strong desire to improve. If you have any tips, I'd appreciate it. Any books (I wanna learn more rhythm piano) would help too. I tried googling "keyboard tutorials' NO LUCK! GRrrr.

On a side note, does anyone know how to modulate a song? Let's say we start in the Key of G and we want to move the song to A to shake things up. Should I first jump to V chord of G (which is D) then right on to A?