i did the engine diagnostic and got the codes 03-07 and 05-03, front right heated o2 sensor and closed loop control. does anyone know how i would go about getting them fixed or (preferably) fixing them myself? any help is appreciated

You need an O2 sensor socket and a 3/8" drive ratchet, and some PB Blaster (kind of like Liquid Wrench but better). Spray the O2 sensor (Make sure the engine is COLD) tap the hex part of the O2 sensor a few time to set up a bit of a vibration and let it sit for a while. Repeat. Then take the O2 socket and ratchet to it and take it out. Of course you'll need to buy a new O2 sensor to replace it. It sounds like your O2 sensor is completely dead if its tripping a "closed loop control" code as well. These O2 sensors are used in closed loop to regulate the fuel/air mixture and will kill fuel mileage if they aren't operating correctly.

If you decide to get the o2 sensor and DYI, you may save some money by purchasing from: http://www.foreignpartsplace.com/

Also, if you want to read up on o2 sensor problems/codes etc., do a search on the .org for 'oxygen o2 sensor' and you'll find plenty of discussions.

Good luck,
AnGe

My experience here:

http://forums.maxima.org/showthread.php?threadid=180024

really... I guess I was lucky. I ordered Bosch o2 sensor from them and I received the order the next day.