Welcome to LGM, His Princess!
I'm in a situation very much like yours...just got done making a background track for the Youth choir to sing Sunday.
I have an older G5 Mac and use Finale for notation, and Logic Express to record vocals and instrumental tracks. Also have a M-Audio 88-note keyboard with a USB port, so don't have to use a Midi interface. Finale and Logic both have learning curves, but they're well worth it - and they have software sound fonts, all digital, so you can record and mix in the computer.
I don't have the most elegant setup (no ProTools or audio interface), but it works.
Hope you are blessed with info and good fellowship here...