lower cam housing seals

Hello,

I have a '98 Grand Am Gt, 2.4L manual transmission. It started running rough, so I had a dealer scan for trouble codes. Pulled a P0300 random misfire. Upon further inspection the spark plugs are covered in soot, and it is running rich. I am guessing that oil is leaking into the cylinders, and I see what looks like oil inside the intake manifold, and around the cam housings. My O2 sensors are probably sooted over as well, which I guess is why my fuel mixure is rich. How hard is it to replace the cam housing seals? The dealer wanted $1500 for the job...It doesn't look hard, but I haven't messed with DOHC engines much...also I tried to replace the fuel filter, which I thought would be an easy job. I broke the 4 tabs that secure the north end of the old filter. (my bad) The dealer said that because of that I would have to replace the entire fuel line assembly from the engine back to the gas tank!? ($700) Sounds bogus, but I just want to make sure. Thanks for any help!