The great oil debate, must be 100 threads about this.
First question about special oil, the truck has sensors and determines the time you should be changing your oil, ie Length of time the oil had been in the truck, how you drive your truck, its present viscosity, etc, etc. If it says change it, I would since its the oil from the factory and it has some cleaners in it.
Once you change it, reset your oil change indicator and you should be good for another 6 months or 8000 miles which ever comes first. but you can change it whenever you want or depending on the oil you use when it should be due.
the Ram 2500 does not have mds, ram 1500 with mds oil specifications for it to run properly is 5w-20. This has been a big debate, I have a thread just on this and at the end of the day its been decided to do what the manufacture recommends. and that is 5w-20
Full Synthetic or Dino oil, this has been the great debate also and you will notice that most members here at the site that want to keep there trucks for more than the 3 year lease or purchase to own type member are running Full synthetic. Some run Amsoil, some royal purple, some pensoil ultra, some mobile, and that is another great debate, one conscious about all this oil stuff is don't use a fram oil filter
Also, if you do your oil yourself, or have someone do it, and its your first oil change, make sure they or you check that the oil filter gasket came off with the old filter. More than one has made that mistake and lost there oil the first 30 feet of pulling out from the dealer, there driveway, the lube dude. JMO