There is no need to have the valves and seats ground if the engine still has good compression on all cylinders. Your mechanic can test compression pretty easily. My Accord has 253K miles with no valve issues and my Nissan 240 has 290K miles and no valve issues.
Checking valve clearance is easy to do, and replacing the valve cover gasket is easy and likely needs to be done anyway.
The ECU controls whether or not the 2nd intake valve opens using an electronic solenoid that allows oil pressure to enter a passage that engages the rocker arm that operates that 2nd intake valve.
The maintenance issue to be most worried about is the timing belt- if it breaks or slips, it is almost certain that the valves would be damaged and this would be a major and costly repair (at least 3 times more $ than having the timing belt replaced would be).
A word of advice/caution. The screws that hold down the valve cover are notoriously difficult to loosen if they have not been loosened in many years. They have a tendency to break at the threads near the end if too much torque is applied while breaking them loose. It's best to use an impact driver to pop them loose before applying torque. That might not even do it. Three of the six screws I loosened on my current 92 VX broke despite precautions. Good luck with yours. The valve cover needs to be removed to change the timing belt.
Yeah, and when the valve cover bolts are found to have been stripped out by the previous "mechanic," make sure you know of a good motor supply place that can sell you the helacoils! They aren't that bad really.
But get the timing belt done pronto, tensioner too, and water pump since you are in there anyway.
Yeah, I think one of the screws are broken already if I remember correctly. I'll just take it to my Honda guy for the belt/tensioner and the water pump. That way he can take care of getting the valve cover off and replace the screws. He mentioned the timing seemed to be 'loose' before anyway.
Thanks for the tips guys. My Honda mechanic said he'd do the timing belt, water pump, drive belts & seals for around $500. I just need to ask if that includes a new gasket since he's apparently going to have to pull the valve cover.