Transmission will not shift into first gear. What could cause this?

Why needlessly replace all these parts when you can actually make things worse by doing so if the parts are not needed? Has any testing been done at all? If you had this problem start after timing belt replacement at a shop, have you engaged that shop about your concern and asked for them to help find out what's going on? Before replacing any solenoids and harness, I'd be retracing the steps of the timing belt installation to see if something is not properly connected. I'd also be using a diagnostic tool to troubleshoot the automatic transmission operation. I'd be monitoring shift commands and the response of the solenoids to see what is happening. As far as the transfer case motor, it's always important to replace parts you know to be faulty before guessing at other things. Whereas it probably does not affect transmission shifting, it's still an outstanding repair that is needed, and unintended consequences can happen.