You know, I don't know who STI would get to do the cleaning, but if you have some non-pinball guy poking around inside the cabinet with a vacuum cleaner hose, you're just asking for some bent switch leafs. Even seasoned folks catch a shirt sleeve now and then (not me, of course!).
I'd be tempted to do the cleaning myself (or find a local pinhead who'd be willing), and take a cash amount for that from STI.