First off - WELCOME to Team Camaro ! [img]graemlins/beers.gif[/img]
The air pressure should be above 80#'s to make sure the valve(s) remain on their seat and do not come loose and attempt to drop into the cylinder bore as you work. Under normal circumstances engines see way more that the 100~120psi most compressors supply so the upper amount of pressure doesn't really matter here.
It is not necessary to have the cylinder at TDC - it won't matter anyway as soon as you put air pressure to the cylinder, unless you lock the flywheel mechanically* in place, as the air pressure will 'Roll' the engine as the piston moves to the bottom of it's travel.
Be sure to "pre-wack" (use a plastic headed mallet) the valve retainers to loosen the split-locks if they have been in place for awhile.
"Do I just attach the compressor line to the adaptor and let ?? pounds of air in and release when the valves are done?" - yup...
All the valves should be accessible - you may need to remove little things like brackets or vac. lines. (well - and of course the valve covers...
Good luck - post back with other questions if necessary and someone here will help out!
note: * If you leave the trans (manual) in gear and use the driveline to hold the engine from rotating make sure the E-brake is set & the car is well blocked and not up on stands where the drive wheels are in contact with the ground.
IT WILL MOVE!