Being a perfectionist would hurt and help your auto related business in my eyes. People make money by charging a set price to do a job......... With me! If it takes you several more hours to do a head job someone else can do in less time, who made out? The quality is the same but it took you two hours more time to do the same job. Even when you own a business, there are still only 24 hours each day.
By being a profectionist your work area will always be ready to work in. You won't see crap laying on the floor. The floor will be clean, tools will be centrally located etc.etc.etc.. You won't waste time looking for anything.
Just because you build a shop, spend money letting everyone know you're in business, doesn't mean everyone will rush to your door to spend money. You'll spend time providing free information. Folks will always want something for nothing.
Buy or build a home with an attached work area. Don't be screwing around building race engines in a single family housing developing. Don't spend the money to rent or build a building until the business can support it.
Jeg's as an example didn't spring up over night. Sr. was, still is, an Ohio racer. All of the after market racing performance companies were in California. So, he started a business building and selling race car parts.
Go for it - start small - keep the paying job - have fun. Too many people set on their ass too many years thingking about doing something they never do. You say you're a prefectionist. Well, sounds like you're smart enough to make a business plan. A wife willing to not see you too often should be part of your plans. If nothing else she can do the books.
An old man and his dog!
Thinking about a buisness.... 
