RCU Forums - Engine Question

I have a jato 3.3 with stock engine. Today i was cleaning up the truck and decided to pop off the exaust and take a look at the engine. I stuck some q-tips in there and they did not come out clean. Then I took off the head and it was not very clean under there either. So anyways before i took it all apart the engine still had good compresion and i do not think any real damage is done. I bought the truck used and the previous owner claimed he broke it in and then ran 2 tanks, and i think i have ran about 3/4 of a gallon through it. So now that i am going to take apart the whole engine and clean it. I want to know what seals i need to replace. I know i need the exuast and the round washer looking thing on the bottom of head. Should i replace any others?

Thanks for any help

Nick