This is a long shot, but a common problem on the automatics is for them to leak fluid from the transmission adapter plug housing. This is the large electrical connector located at the front passenger side of the transmission. According to the following post on a Sprinter forum (Sprinter vans have the same transmission), this plug could also be related to your problem of being stuck in first gear.

Stuck in 1st gear - Sprinter-Forum

If you do have a plug leak your transmission may be low on fluid. Unfortunately Chrysler didn't provide a dipstick and the filler tube is sealed with a locking cap. The good news is the replacement of the leaking adapter plug housing is not all that difficult if you are mechanically inclined. I replaced mine while changing the transmission fluid. You can get all of the parts needed including fluid at the following website....

Transmission Fluid-OEM Fuchs 4 Liters 2002-2011

Finally, here is a link to a great post from waldig describing the replacement of the leaking adapter plug housing....

https://www.crossfireforum.org/forum...-ta-daaaa.html

Hope this helps.