problems after valve cover replacement

While driving my car for the 1st time after picking it up from the repair shop, I notice its running rough, skipping here & there, seems to be idled a little too high, and I thought i smelled something burning.(I live approximately 45mls or so from the repair shop.) Stopped at a gas station near my home, raised the hood & saw a wide pipe-like structure at the front lower end of the motor that looked was glowing red as if it were "fire hot". None of this was happening before I dropped it off..i wasn't having problems, I just needed my oil leak repaired. I picked it up right before the shop closed & its Friday, but im going to take it back on Monday, just wondering what the possible diagnosis may be.