For the now old body style of Dodge Ram's, you can now upgrade your OEM radio to a double din navigation unit. Here is how:
First, you will need to visit your local Dodge dealer / dealer parts department and purchase a new plastic molding piece for your truck. It is very important that you do not provide your vin number or you will get a new piece that matches your existing trim. Tell the parts counter representative that you have the "MyGig" Navigation system for your respective year of Ram. I called my local dealer and got a price of $103. Crutchfield calls the configuration of Ram with the MyGig system a "premium sound w/nav and 7 speaker sound"
Second, you will need to find the double din nav system that best fits your needs. I have done my duty and found the best for my needs. If your like me and have a "smart phone", the right head unit can give you the capability in conjunction with your phone to stream music and make calls with Bluetooth. If you choose to upgrade in this manner, you will never have to pull your phone out of your pocket again to get into your car, or when a call comes in. You can even listen to music right off of your phone. This is one feature that your passengers will like because you can now hand your phone off (ok, so now you have to take it out of your pocket) to any passenger in the vehicle and essentially turn them into a DJ. Your friends don't like your taste in music? No problem, if you in a 3 or 4G area, download new songs, and in seconds, you can have new tunes playing over your car's sound system without a single wire. Plus, if you follow my recommendations, you now have Nav unit that will fade out the sound of your music and give you directions, then when they finally shut up, your music fades back into existence and your rocking again.
Now, for a side note. The ability to make and receive calls using Bluetooth pairing between your smartphone and compatible head unit is an AMAZING convenience, but selecting the wrong head unit can turn it into a nightmare. I would highly recommend finding a head unit (if the one that I selected and linked below doesn't fit your needs) that you purchase one with a WIRED microphone. I have had to return 2 head units with the BUILT IN microphone because the only thing heard on the phone of the person I was talking to was road noise. SO.... BUY THE WIRED MICROPHONE unit.
Now, for the product. Wired mic, excellent Nav interface, Free updates for life, competitive price and a very reputable brand, this JVC offers a knockout punch over the competition. I linked it above, and I have to tell you that today (4/16/11) is the cheapest I have ever seen it.