[welch-time]

Depends on the age of the last roofing job and the condition of the shingles.
If the shingles are less than 5-10 years old they should be able to be removed individually, repairs made to the underlying sheathing, then replacing the felt paper and shingles. If the shingles are well sealed and brittle, it can be challenging. I've done it myself, replaced some rotten plywood along the rake edge of my house where water was wicking under the drip edge because of improper shingle overhang. Roofers just don't like doing small jobs. I hate dealing with contractors, so I end up doing a lot of jobs myself. I'm going to be doing this at our cottage soon where I have to move a wood stove chimney pipe, flashing, etc. Should be fun. You just need to find the right guy. Maybe ask around for a good handyman with roofing experience. Most Handymen aren't very good but sometimes you can find a retired carpenter with roofing experience who prefers small jobs. It ain't rocket surgery.
Just remember, If any roofing guy show's up with a big bucket of tar, send him packing...