If I remember correctly, the original egr valve was a poor design and was replaced at the dealer whenever these cars appeared for service. The updated valve looked the same as the old, so a red dot was painted on the new egr valve to let other mechanics know this work was done.
There are a few easy things you can do before throwing expensive parts at the problem. The problem egr line is not the thin line you saw, but the 1/2" diameter line that snakes behind the head to the intake manifold. The problem area is typically confined to the first few inches of pipe at the intake manifold where deposits accumulate and needs to be cleaned out. This can set a Code 5.
The other easy thing is the egr valve itself. Apply vacuum to the fitting and see if the valve responds. If there's no movement or if vacuum doesn't hold, the valve needs to be replaced. With the valve removed from the engine, try to blow air across the port. If you can blow air, the valve doesn't seat properly and the valve needs to be replaced. After doing these tests, you'll want to wash your lips before eating
I can't think of anything in the egr system that would cause plug to become wet with fuel. You're probably looking at more than one issue.
Depending on you level of confidence, changing the engine wiring harness is not that difficult. The part itself is expensive.