i just painted my IMRC red last week. I took it off, washed it with soap and water til it was spotless. I used dish soap to get through the grease and stuff. Let it air dry. Then i picked up a can of plastic primer spray paint and the can of red plastic high gloss spray paint. Did two light coats of the primer and let it sit in a non-humid(my deck in the sun) place for 2 days. Then i did a few coats of the red, let it sit for a week and put it in. It came out very nice.
I was worried about the paint not being a hi-temp paint but its reacted just fine after two weeks under the hood. No bubbling or cracking. Ill try to get some pics up for you to check it out.
When you take the UIM off to clean it, clean it out with some thottle body/carb cleaner. Spary a crapload in the intake ports and let it sit for a while, then wipe it out and do it some more til you can actually see the silver of the manifold. I toothbrush will work well scrubbing it. While the UIM is off, spary the lower intake manifold ports with the throttle body cleaner also and scrub them with a rag. Just becareful of not letting anything drop into the open intake ports.
As for changing the gaskets, you definetly should. I swapped in the SVT UIM and TB a few months ago and the gaskets were pretty much disentegrated, even with only 55 K on the car! Check out the CEG forums(contour.org). Theres a real good how-to on doing the UIM rebuild/swap.
If you have anymore questions, feel free to PM me. Good luck man.