I would look at the National Electric Code before starting on a 50 amp installation, regardless of state.
Just know that you can do the work without pulling a permit, but it may be an issue if you later sell the house...I am in california, just wondering if there is any regulation around installing my own switch or upgrading one if it exists in the garage already?
Just make sure it meets code at the time you do the work.From a search:
Can a homeowner do their own electrical work in California?
A property owner may do electrical work on his own property; B. A homeowner or a member of his immediate family may do electrical work on his residence. 070 – California Electrical Code—Amendments—General.