If you are anywhere close to handy, both these jobs are very simple and easy. You do have to be able to crawl under the rig though.
The $150 sounds reasonable for an RV dealer quote although that is still very high for what you get. The job requires a couple gallons of oil and two filters. Labor is small.
If that quote was for both jobs and you are not interested yourself, go ahead forward as you prolly won't find any cheaper at dealerships.