golf won't shift out of first.. HELP with troubleshooting

ecently bought a 2005 golf tdi automatic to make into my daily driver (this is my first vw), car will not shift out of first gear and has check engine light. upon getting the car back to my garage i discovered tranny hadn't been serviced properly. i properly serviced the golf and was hoping this would help get the car driving while i gather parts needed for swap but no luck car is still not shifting and throwing check engine lights. it is a theory of mine that due to being in properly serviced that the car put itself in to safe mood to protect itself. is there anyway i can test this theory. Also looking for help with troubleshooting. i was aware of a transmission problem at time of purchase and plan on doing a swap but was hoping to get it driving for a month or two any advice or theories would be appreciated.

You'll need a VCDS (or equal) to go much further.
KansasCityTDI.com has some good tips for auto transmissions. Forum member CoolAirVW, very helpful.

plugged a VCDS in to it and it was throwing check engine codes and a transmission code. ill have to plug it back in to get the exact code it was throwing.