My current TV is the first diesel I had ever owned. Since I bought it used with no warranty, I purchased an extended maintenance agreement. I asked every friend, acquaintance, even in-laws, that I could think of that had diesels, who they went to for maintenance. To a tee, they all mentioned the same independent garage in our town. I hooked up with them and have been extremely satisfied.
Now, that extended maintenance agreement I mentioned earlier is a whole "nother" story! If you plan on entering into one of those, take a couple years and READ the fine print about what they do and do not cover.
Good luck, my friend.