Valve clearance is measured with a feeler gauge between the rocker arm and the tip of the valve. However, you must inspect the tips of the rockers to make sure that there is no groove worn in them which gives you a false reading. I have replaced a lot of valve guides with a hydraulic press. However there is always a risk of cracking a head if a guide does not yield soon enough. Most people these days prefer to have the guides reamed out and a sleeve installed. I have a 50 year old Sioux valve machine for refacing valves and then grinding the tips an equal amount as removed from the face. It also has a rocker arm attachment. I use an old fashioned stone type grinder for the seats, but I measure them with a runout gauge. But this is really machine shop work. The term sticking valve means that varnish has accumulated on the stem and does not allow the valve to travel freely. It is usually caused by stale gas. Measuring guides is rather simple, but it takes a valve compression tool to remove the valves, a mike to measure the valve stem and a small hole gauge to check the guide and check it for being bell shaped. This is probably more than you want to do. I still think you should remove the spark plugs, squirt some Marvel Mystery oil in each cylinder, let it set for a week and then turn it over and see what happens.
