Rebuild for an otherwise good caliper is straightforward. A compressor/pump is useful for popping out the pistons after the caliper is pulled.

There's a bit of fussiness involved to get the outer seals, like your torn one, situated. It's like trying to stretch the too-small rubber band around the groove.

In Boston, assuming standard wet roads, etc. I'd recommend sooner rather than later. You "might" be able to just replace the outer boot, but I think the procedure for getting the folds and the seals the right way round calls for putting the outer boot on the piston first, then inserting the piston, then snapping the boot onto the caliper. I'm going from memory and could be wrong. If correct, that technique seats the inner seal from the boot to the piston correctly without too much finagling. The other way may also be possible, just with more finessing the boot into the ring.