It only has one slot for processors so I would say it supports only one. Save your old processor in case there is a problem with the new one so you have a backup in the circumstance that you become computerless.
No, it does not support 2. As far as throwing out the old processor, How old is it???? If nothing else put it on eBay and sell. Might be worth something there. I tend to keep things like that so I might not be the best person to ask, lol