A close friend of mine opened a DIY shop outside of Minneapolis. I used it several times. Especially after track days when I change fluids, brake pads all at once. I've worked on several friends and family cars there as well.

http://firstgeargarage.com

It’s a great idea, but your scope of offerings is going to demand so much overhead that to me, it doesn’t sound sustainable. I would focus on the broader appeal rather than on specialty areas cause the one ore two people who come in each week or month won’t be covering your costs.

Insurance is available. It might be hard to secure but reasonable policies are out there.

You will need a large marketing budget though. Getting the word out and breaking down trial barriers is very difficult. The enthusiast crowd will generate so much business but you need the other 90% of your target audience to come from elsewhere. You might even consider franchising as much of the marketing effort has been established and the business model is in place.