Can we swap a 5.7 in a 2005 Durango with a 4.7? I blew a head gasket, a perfect opportunity to upgrade!?

Yes, check some of the mopar forums, it's a common upgrade, just entails swapping more than just the motor. Normally a motor swap would mean swapping out wire and engine harness and engine computer as well, however I had heard that the PCM may be kept from the 4.7 and just reprogrammed and even the engine harness could be kept as it was very similar to the 5.7. The TCM (trans module) would need reprogramming as well. Exhaust and linkages would need reworked. Again, find a "how to" on a Dodge forum, lot of people have gone this route.