For the headphones I would look into a pair of HD 558s. They are really comfortable and should work well for gaming. However I would recommend to at least try them out before you buy them. Their sound profile isn't for everyone. My local bestbuy has a Magnolia section and they had several Sennheisers on display including the 558. I'm not sure about yours.
For the mic you could look into any cheap 3.5mm boom mic. It should work fine. If you can stretch your budget an Antlion Modmic ($50) would be ideal.