I wouldn't...in my opinion it's too risky. My friend's car started misfiring after doing his. To be fair I don't think he protected the electrics properly.
When I first bought my car, my engine bay was not in good nick either. I used Autoglym Engine and Machine cleaner and Autoglym Vinyl and Rubber care, the engine bay looks nice and clean now.
I just make sure I keep on top of it every couple of months.