a couple thoughts from a tech's perspective:
First off, when you come into posession of some type equipment and it may need some repair(s), it's wise to look at the value of the equipment. Is your B6100 worth what it costs to repair it? If no, you can give it to someone else and advise them that they'll need to spend some money on it, you can fix it yourself, or you can sell it. Those are the most popular options.
Secondly, a lot of dealers don't really care to service/repair older equipment. I'm one of the exceptions. So what they'll so is estimate really high in hope that you'll not fix it. But why? Because techs a lot of times get a bonus (based on billed labor) or they work straight commission; both cases their best paying jobs are the smaller jobs like PM and radio installations, and any internal stuff such as but not limited to assembly & prep, loader installs, etc. They love those because they can do them in half flat rate, so they make money on 'em. Older equipment there is always the risk of breaking fasteners, breaking parts that are NLA, and the dreaded fix-one-thing-something else breaks problem, which NO tech likes (and neither do owners and that's why the techs don't like them). THOSE can be nightmare jobs. For instance years back I was doing a clutch in an L210, quoted the job, ok'd, then I jumped in. Flywheel bolt broke during removal. Hard bolt, drill bit was like trying to drill a piece of diamond, the bit never even dented or scratched it. Got a hardened bit, it was the same way. So then we had to call the owner & explain to him that his old tractor sometimes those kinds of things come up. 'Course owner has no idea, he's upset (and rightfully so), we're upset, tech's upset, shop/business loses money and makes a would-be customer mad, likely to never see him again. That's the kinda stuff you get into with older equipment, and I'm NOT making it up. The key (for a tech) is to do only the bare minimum and charge accordingly, and sometimes that becomes a surprise to the owner even after being quoted. It never goes as planned.
Very similar to old cars. There is a reason old cars are expensive.