When you say your experience is in "logistics" that doesn't tell me much, but by you're own admission you are "new" to any heavy repair. Sounds like your partner is the mechanic, and you are hoping to ad a lube service with it?
I'm guessing from what you've said that you are partners in this deal? You're the $ and he's the labor/ experience?
I'm not asking to try to get personal, but to give much for advice, I'd need to know a little more about what you're trying to do. Are you just answering the phone, and dealing with the paperwork/schedule, while he's out turning wrenches? Or are you hoping to turn wrenches too, or help?
I will say this much, its really hard to be the man in charge, if you have no idea what you're doing. If you're the guy answering the phone, its going to be hard, because the guys on the other end, want to feel like you know what you're talking about.
Its going to be hard to estimate how long jobs will take, because you have no idea. It's going to be hard to tell the guys that are working for you what they need to do (if you add employees), when you don't know what they need to do. Or if they're really milking the clock on a job.
I could see it working one office man, one wrench turner, but I think you're going to have a hard time generating enough $ off of that to keep both of you fed full time, by the time you take out the insurance, taxes, workman's comp, and fuel and all the other stuff. Its kind of like a buddy says about dump trucks, you need to either have just one truck, that you drive yourself, or you just as well have 10 trucks, as only having 2, because the paperwork is the same, but the money coming in goes up. But I wouldn't wish 10 dump trucks on anyone.
Good luck, its the american dream to own your own business, a lot of guys on here do. There's a ton of great advice here that you couldn't pay for, and you won't find very many situations, that someone on here hasn't seen before.