As a former professional Ford mechanic, I will chime in and say this:
The guy should call and tell you what additional stuff he found and give you an idea what it might cost.
As a mechanic, I had customers that never questioned my work, if it was broke, fix it, they didn't have time to be down. Never did anything that didn't need to be done right then. If it could wait, I told them the deal & let them make the decision.
Yet other cusmers would bring in a car for repair of say a leaky power steering hose. Mean while, you've got rotted & bulging radiator hoses, belts with chunks out of them and a dozen other things that needed urgent attention. You replace the power steering hose, tell them about all the other problems, they nod at you like your trying to sell them something and they go on their way. They come back a few days later and bitch at you because you didn't fix the other problems.
Further up the asshole scale you'd get cheap ass fucking pricks of customers that would bring in a rattly rolling pile of shit to have the very bare minimum to get their ass down the road/ pass inspection. You'd fix exactly what they wanted, exactly how they wanted it fixed. Blowed out muffler? muffler tape and coat hanger was all they wanted done. You'd make the repair %100 to their specification & financial understanding. They'd pay and the next day be back bitching to high heaven that you fucked up something totally unrelated to the repair and then damn well expected you to repair it free of charge.
Boils down to this, if you can trust the guy and he is looking out for your best interest & safety, then work it out. If he is selling you shit like nitrogen fill for your tires, power flushing your engine block & transmission, teflon paint sealant, new platnium spark plugs before 100,000 miles. Then he's trying to make a buck off of you. It sounds like you run the shit out of your vehicles, so it probably really needs what he is suggesting.