Any mobile tech should be able to handle the checking. However, some will opt out of anything related to waste tanks. Most of the time, a cracked black tank cannot be successfully repaired although some have done a plastic welding to repair the problem.
Good luck and hopefully it is just a small leak at a pipe joint that can be easily repaired. The belly pan will most like have to be dropped to get to the area.
Ken
Amateur Radio Operator.
2023 Cougar 22MLS, toted with a 2022, F150, 3.5L EcoBoost, Crewcab, Max Tow, FORMER Full Time RVer. Travel with a standard schnauzer and a Timneh African Gray parrot