2001 VW Jetta error code

Ok, so here is the deal. i have a 2001 VW Jetta 1.8 turbo stick shift, 99xxx miles. The car had been sitting for about a week. I am a dealer but I am trying to get out of the business. one of my drivers had the car for a while and he told me that the car would run fine and then all of a sudden run bad. So when I picked it up yesterday, to my surprise, the car was running like a dream. Turbo was boosting, it had pep and it drove great.......for about 20 minutes. All of a sudden a the EPC light came on and the little triangle warning light. I had power loss and it started sputtering(misfiring). It drove ok on the highway but you can tell something is wrong, especially in lower speeds. So here are the trouble codes with the meanings:

P1176 O2 Correctionbehind Catalyst, B1 Limit Attained
P1297 Connection turbocharger - throttle valve pressure hose
P1103 O2 Sensor Heating Circ., Bank1-Sensor1 Output too low
P1171 Throttle Actuation Potentiometer Sign.2 Range/Performance
P1542 Throttle Actuation Potentiometer Range/Performance
P1545 Throttle Pos.Contr Malfunction
P1568 Idle Speed Contr.Throttle Pos. mechanical Malfunction
P1602 Power Supply (B+) Terminal 30 Low Voltage
P0102 Mass or Volume Air Flow Circ Low Input
P0300 Random/Multiple Cylinder Misfire Detected
P0507 Idle Control System Higher than Expected

I would like to fix this myself but I would like to have a game plan. I am noticing a lot of O2 sensor things, throttle control or position(maybe the sensor), maybe the mass air flow sensor. Is there one thing I should try first? Is there one thing that would set all the others off?