If by "plenum" you mean the upper intake then yes, any good mechanic will replace that gasket while they're in there. Have them inspect the EGR and coolant passages of the plastic upper intake as well. If it hasn't been replaced since the factory it may have issues there. That was a common problem on this engine.

They replaced the upper & lower intake gaskets, heater/coolant bypass tubes/pipes, thermostat & gasket, coolant, oil & filter (synthetic). I had the front & rear brake pads replaced (rotors turned). It'* so nice to not have that pulsation/vibration when braking.

There'* still a MAP sensor setting a code, which I'll have them check when I take it back next month.

When I first got into the automotive field the mechanical labor rate was around $16/hr +/- and jumped to $18 not too long after. The Buick dealer I went to was at $135/hr. That was a shock to me but I had anticipated it, saving my duckets for all the above repairs. It still has about $3000 more work to be done in window regulators & motors, as well as some body electrical work involving a scrambled DIC display and related cluster readings.

Wow, you're putting a lot into it. It'* going to be a new car soon!

I know. It was a tough decision. I've been shopping used cars for several years and later models are way out of range for me. Even the lower priced models which I could afford the payments on, I couldn't afford the added costs of increased insurance. I know my car has been very reliable these past 8 years. I have seen quite a few cars similar to mine for much lower prices, but I wouldn't be comfortable not knowing their actual mechanical condition.

Sounds like a good plan, plus the others (that you don't know the condition of) might also have some kind of hidden problems that are the reason the previous owners got rid of them.