i would almost lay money that the noise is the coupler going bad. get a ZZP coupler, they are the best ojn the market and it is very common for them to go bad and make noise. but still check the fluid level , there is an allen plug near the nosecone that you need to remove to check the oil level, and yes, it is a special oil that you can get from GM
you can get both the coupler and supercharger oil at this site,www.zzperformance.com
they have the best coupler on the market, the noise will be a rattle like noise at idle and depending on how bad it is, it may continue farther up into the rpm range. this coupler is a rubber disc that takes the shick out ot the nose drive to the rotors.
very common for them to go bad
Don't forget the techinfo article which explains step-by-step how to change the front end of the supercharger. Some users here have had problems with leaking supercharger oil after changing the coupler. (I would put the link to the article here, but i'm still learning how to use the tags on here)