There is very little difference between NON SYNTHEDIC diesel motor oil brands as long as they have the same viscosity rating and the same API, CH-4. Although I wouldn't recommend mixing brands, using different oil brands between changes should not cause a problem. I have had oil changes all over the country, and it seems they used a different brand every time. Rotella is my first choice, but I have no real data to justify that. Doing the job yourself should not be difficult as long as you have the right equipment and you follow the procedure. As to the frequency, 5,000 miles is not an unreasonable distance. My Cat manual states 11,000 for medium duty and a 24-quart reservoir or every 6 months. I generally go for a year and no more than 6,000 miles. Most all of the diesel mechanics I have talked with agree with this frequency. I am very curious to hear from some pros on this one.
