If you replaced the front head gasket, there is not a lot more to replace the back. When I replaced mine, I knew that there was a leak at the lower intake manifold. I decided to do both head gaskets because I was already there. I'm glad I did that because the passages were caked shut with dexcool sludge and maybe some stop leak. When I asked how much it would cost, I was told ~$1000. If I ever have the problem again, I will probably end up paying someone to do it so I can get my car back quickly... (it took me 4 weekends in 35 degree raining weather conditions partially under a carport).