Think of it this way:
If you had a painting business, would you call it Don`s House Paint???
Putting two nouns together, the second being implied, meaning it could be interpreted as a noun or a verb, (Auto and Detail) after a singular possessive person (Don`s) just does not sound good nor is it "proper" English. My Mother was an English teacher and her key method of understanding how to construct sentences or phrases with proper English was to read it out loud AND/OR rephrase it with similar terms and see if it sounded OK and made sense, which is what I`ve done with the "paint" term. The addition of "- ing" to the word "detail" makes it an action verb, leaving no implied interpretation of what you do. Sorry to be so "technical`.
(I guess having my Mom as an English teacher for my junior year in high school wasn`t a total waste of time after all. However, if she found out that I thought it was a "total waste of time", I`d be on writing a 500-word essay on "What is Good English" as punishment and it would be due by tomorrow`s class! Now can we move on to correct punctuation?? (or is it "Can we move on to correct punctuation now??) Keep laughing!)