It was mostly dust and dirt. I took it to the car wash and sprayed the whole engine bay to get rid of all the loose stuff. Then took it home and used a little Sunlight dish detergent and scrubbed the areas that didn't come clean with the spray down. There was very little oil or grease. I bought this Sonic Scrubber Pro Detailer. Its like an oversized electric toothbrush with a bunch of different heads. After everything was as clean as I could get it I used some Armour All on all the plastic and rubber. Turned out better than I thought it would! I let it go way too long!
Here is a pic of the Sonic Scrubber