| Hal Leonard has some Bass version Praise & Worship books out, but honestly, they haven't helped me much. Our praise band only plays a few songs out of each book and not usually in the key the book uses. (Have to work around the singers ranges.) I mainly use the books to learn a few embelishments here and there.
Here's how I, and actually, the whole praise band I'm in at church, have learned all our music (60 songs and growing). Someone finds a song they like, we look it up on the CCLI site (ask if your church subscribes - you can get most popular worship music there as long as you are using it for worship at the church), print a lead sheet (with chords) in whatever key necessary for the singers, then find an mp3 file or youtube video of the music and lift our parts. I usually work mine out ahead of time as much as I can because I have a hard time hearing the bass lines and like to play with the equalizer and use my noise-cancelling headphones so I can hear them better. (This is all very challenging for me 'cause I'm first and foremost a sight-reader and would LOVE to have my part all written out and handed to me!)
First step for you really would be to find out what they play at your church and go from there. Sitting in with the band will give you a good idea of how they play the songs, too. Ours always seem to end up a bit more on the rock side than the mp3s we listen to. The church next door to us plays some of the same songs but with a much smoother and more traditional? feel. Hope this helps! | 
