Repairs are actually not that difficult. I used to do all none warranteed repairs for the City of Boulder’s 3 rec centers and several small city workers gyms. You can find a lot of the information on doing the repairs on line. You can also request assistance from the manufacturer. Many will supply instructions and tech support for small fees or free. When I was in Boulder I couldn’t believe the cost of having an outside service do our repairs. So I offered to take on the repairs of anything no longer under warrantee. It probably saved the city tens of thousands of dollars while I was there. It is very likely that someone on your staff has good repair aptitude and skills already. But no one has bothered to ask. If you still prefer to get an outside service. I recommend calling around to your competition and ask who they use and get their opinion of the service.