Wooooaaaahhh there! Dont get carried away. Acertain that the heater matrix is at fault before even considering removing it. Disconnect the two pipes that go through the bulkhead first and attach a hose, try it on both pipes to to make sure there is a good flow. I would suspect that it is no more serious than an air lock, these are easy to get if you dont bleed the system properly after draining.
If you read the Rave manual to see about removing the matrix you will have heart failure. There are short cuts that are well documented to make life easier.