First of all, isolate the noise. Pull your Alt and A/C belts off then start the car and try to find the noise. A lot of times it's the belts or an idler that you may be hearing. If the noise is still there, then you have another problem that could potentially be something major.
As far as the oil light problem, it could be a couple of things. Worst case -- sludge and/or oil pump.
Another possibility is the sending unit/wire. There is a TSB (NOT a recall) for this problem. It's #08-36-99 and requires modifying the wiring at the sending unit. You'll need to purchase part #5017800AA and the part runs about $18. If I remember right, they charge 0.2 hours labor to do it for you. I'd also replace the sending unit which is part #4608303AB and runs about $14. IF you're not having an oil pump problem, this should take care of the light coming on at low rpm. HTH