If you only have one programmed key now, you will need a dealer or locksmith to program another. When I bought my GT, it came with only one key but I found a local locksmith to program another at a much cheaper price than the local mitsu dealer. Once you have two programmed, you can program a third by yourself. If I were you, I'd call the dealer to get their estimate, then call some locksmiths to find a better deal. IIRC, I only paid about $30 to get one cut and programmed, plus the cost of the correct key from ebay (~$10).Took the GT in for a smog inspection today. It PASSED ! ! Makes me feel good that I sorted it out. It had not been licensed since 2017. It is still a work in progress. Needs some A/C work. I think it will need a clutch sometime in the future, and I want to add a modern sound system. I also got it's alarm system and door locks working this month. Had a second key made but need to look into progamming it. ...J.D.
I keep an unprogrammed spare key in my wallet in case I lock my keys in the car, while my second programmed key is locked in a safe at home.