I've been away from the bass for a little over 3 weeks and I have to play (with 2 days of practice) a fairly difficult lineup (for me). Would you suggest just trying to get as much in on the songs as possible (mind you, I'm familiar with most of them) or some specific things apart from the songs to get everything back on track as fast as possible? Please post some specific examples if you're for the latter.

Just start with the root notes for the chords of all the songs. As long as you know those you'll never be lost and you'll be able to add a 3rd or 5th here and there...good luck.

Look (or listen) through the material, find any difficult passages and work on those. Don't waste time practicing the easy parts.