I may have come to this too late, today being Saturday, but you didn't specifically say which Friday so for what it's worth . . .
Beyond the very thorough list above I've found that asking, "Are there any questions I should be asking you but that I haven't?" often brings out some interesting responses. Usually they are small things, "Oh, I forgot to tell you about . . ." kind of things but occasionally it is a big thing.
If you find there is a long pause and the owners are casting quick back-and-forth glances at each other you'll at least know you've struck a nerve and that there may be something amiss that they haven't disclosed to you and you'll need to start digging. If you have to start digging then everything they've told you up to now would have to be suspect.
I would expect you've spent a lot of time in the shop and know the customer mix but I'd ask about unique or problem customers. Also in building the business I'd ask them what they have tried and what did and didn't work. What didn't work for them may work for you, and vise-versa, depending on who you are and who they are, but you might find some patterns in what did and what didn't work. You'll know what positives to continue pursuing and what negatives to avoid or maybe try later in your own way.
Finally, even tho' your excited to get going and get in, don't be afraid to walk away. I was afraid once and plowed ahead even tho' the little voice inside me was yelling 'STOP!' my heart overruled my head and it cost me quite. An expensive lesson to say the least in more ways than one.
Best wishes on the new venture!