Here is my take on this: The 400 constitutes about 6 hours of labor, at a reliable shops rates.
After that be prepared to spend a few thousand dollars for actual repairs, such as front end work,shocks, tires, fluid changes, belt changes, brake repair, general safety items,etc, not including the interior. If any of this has recently proven to be done, consider yourself ahead.
If this same shop will do this work, I would negotiate having the $400 or some of it applied as a credit to the final bill. If you are serious about RV'ing, you'll be wise to have it done before hitting the road. I did that, and feel happy about the expenditure and a lot safer too.
Good luck, my friend.
carson, FL.