u can check valve guides when head is disassembled - basically your looking for excess play and clearance (you need some for expansion reasons but too much will let oil through and go out your tailpipe). If you like to rev your engine to redline at every other stop light, you probably will need guides cause they wear out quicker from that kinda stuff. Cylinder head work is best left to the pros... it sucks pulling apart a D16Z6 head cause there's a lot of small crap in it, plus in order to properly look at everything, it has to be clean, especially if you put it back together to rebuild. As far as the oil pump goes, you can just take it apart and inspect the gears for scoring and wear, then check for proper case clearance with feeler guage. Chances are there's nothing wrong with it, especially if your vtec was still functioning ok since it takes 55 pounds of OP to switch the solenoid. I've yet to see a bad OP in a D16 motor. I highly recommend cleaning up the ports and doing a mild porting job on that head - it make a pretty big difference on those motors. They don't breath that well on the exhaust side, cause vtec is only for intake. If you end up taking everything apart yourself be sure to mark everything very carefully as to where it goes.