I think you should get a more solid commitment from your friend or do some research on doing a build, it's relatively easy but it's nice to have someone help the first time, especially if you're dropping 2 grand.
This is a totally random build but I think it's pretty representative of what you can/should get for about that much if you have to buy everything:
Intel Core i5-3570K, Asus Radeon HD 7950, Corsair 500R Black - System Build - PCPartPicker