you can see what type of heads are on it, there will be a 2 for 2V or 4 for 4V printed on a corner of each head..
the cam, you will need to pull it out of the motor, stroke, there are some threads that tell you to measure the stroke of it, you pull out one of the spark plugs, put a wire down etc.. i wont go into it, as its all detailed somewhere in the forums, do a quick search
compression, im pretty sure you would need to pull off the heads for that too
whats the actual engine doing to 'play up' ? maybe some guys on here can give you a diagnosis if you tell the symptoms..