User Andrews advice is spot-on. I would add that once you've established what appeals to you at the music stores you might consider looking for what you like in the USED market-place.
Worship music is an exploding genre. More and more church's are appointing/hiring music directors and putting in really nice sound reinforcement (PA) systems. Some even hire musicians. I've heard several church music sections and they've all been very enjoyable to watch/hear.
Almost any guitar will serve your purpose. Just get one that YOU like. The AMP is a little different story. The worship bands I have heard actually play with considerable volume. You'll need an amp with plenty of clean headroom so you can crank it up some without it breaking up (getting fuzzy). Little practice/student amps won't work for you. You're filling a large room at substantial volume so you'll need plenty of wattage. That's why I think USED may be the way to go. ((IF ur church DOES have a PA you can get by with a smaller amp with a line out and the PA can do the hard work))
$400 is going to be a bit of a challenge but if you live in/near a major market and you watch craigslist diligently/patiently you'll likely come across a rig that will get you through for several years. Good luck smooth- have fun with it.