What can I do to extend the life of a 83' dodge transmission that has grey transmission fluid?

The van itself runs good. Transmission doesn't slip and it shifts cleanly into drive, reverse, park. Drove it last weekend fully loaded through the mountains to steamboat springs, CO. Went 320 miles round trip and over 4 pes total and it ran great the whole time. I check the fluid when it's running and its grey. When its not running the color is closer to black. Took to a transmission specialist and they said that there was little metal pieces in the fluid and thats why its grey. They said it would eventually fail. What can I do to extend the life of this 83' dodge ram van transmission? I know heat is the #1 cause of transmission failure, would getting a cooler for it help? What about dropping the pan and changing the filter and filling the pan with new fluid? Heard that changing old fluid out can cause the to fail as well?