That was me at my current job several years ago. The guy basically left a landfill as an office for me. It took all summer to go through everything. Library was a disaster. I wound up going through every piece in the library individually and sorted them to see what we had. By the time I was done, we had fewer than 30 full band pieces that could actually be used.
Like someone else said, just do a little bit at a time, even if it's just one really small, insignificant thing per day. They'll add up over the long haul. Some days I'd fill up a trash bag. Somedays I'd sort through a few inches worth of music to make the mountain just a bit smaller. It was worth it when you consider where we are now compared to then. Hang in there!
Previous director drops small school program like a sack of something warm and smelly, I get hired a week before band camp to take over.
Can't walk through the office because there's stuff piled EVERYWHERE, payments have not been made to the camp for band camp, internal accounts were never deposited into as they should have been, there's no drill for the marching show, the library is 20 years past due for organizing, I have no databases for inventory, library, or uniforms, percussion can't read or play (THE PREVIOUS WAS A PERCUSSIONIST!), and the 6th graders (playing since 5th grade) don't articulate.
Nothing is done, nothing was left to help ease the transition. I've gone through 20 pairs of vinyl gloves sorting the library. Just sorting, no database yet. (When that's done, it will probably be the best-stocked library anywhere) Instead of sorting anything, previous director just bought new stuff or got copies to add to the pile. I think I've recycled about 100 POUNDS of paper, after going through it for originals. Oh, and there are two large bins full of misplaced scores. I have no idea what music I have, but at least now it's all alphabetized and categorized so I can at least check.
Please. No matter how you feel about the terms or your moving or your relationship with administration, don't take it out on the next guy.