I have a 2003 Ram 2500 4 door, 4wd. It's a 2500 with about 170k on the odometer and I think it's time to change the trans fluid
How hard/time consuming is it?
Should I take it to a shop and also have them adjust the bands?
I believe your truck has a 545rfe transmission, although it might be a 45rfe. Basically though, they are identical transmissions with software changes. So it will be the same service either way. There are no bands to adjust.
Here's a write up I did, it's pretty easy with basic tools: