Do you have the wireless key, key with remote entry fob or just a regular key? If you just have a base model with no power options, a regular key might work. If you have the fob or wireless key, the keys themselves are cheap. You can program the car to respond to the fob yourself, but not the key. It's programming the key that makes you bend over. A local locksmith should be able to do it cheaper than the dealer, but it's still around $80 to $100 each.
It's not something you can do yourself or have someone do online because you need the car programmed to accept the new key and fob. The car sends out a wireless signal and the transponder chip in the key responds with a code. The car then checks to see if the code is on its list of authorized keys. Entering the code into the car's memory involves plugging a proprietary programming module. The module is only available through Nissan to authorized dealers and locksmiths.
Once you have the keys, for god's sake don't lose them. Watch them like they were a stack of $20 bills, because they are.
