Is the transmission 2000 Dodge Durango R/T 5.9 dead?

It's most likely solenoid related, depending on how long it's been giving you trouble will depend on what else is hosed up. I had the same problem with a I bought truck about 8 yeas ago, the previous owner told me about it. I took it directly to my transmission guy and 1200.00 and 2 return trips to replace defective solenoids, it's running great.