I need to replace a tub and shower valve assembly in my bathroom (the tub faucet keeps dripping and it seems to be impossible to just repair it). I'm wondering what would be the reasonable price for this job. It involves, of course, opening up the wall behind it... I just got an estimate from a plumber that is way more expensive than what I had expected. Any ballpark figures? Thank you.

First time plumbing work need some help. Just found out that my bager garbage disposal is leaking from bottom, dripping slowly close to the reset button area when there is water down from sink. I probably just gonna replace it since google is saying leaking from bottom pretty much declares death. my questions are : when choosing replacement unit should i go with the same brand so that i could just swap the unit without major tubing or mounting work ? Or based on my photo , it should be an easy diy? I only work simple jobs on cars so i may not even have sufficient plumbing tools and supplies. any input is appreciated. Thanks.