Not in Maine, but I did my prebuy in Plymouth MA, just south of Boston at Yankee Aviation. I’d recommend them for both your prebuy and annual. I almost wanted to fly there to do my annual this year as they quoted me $1000 less than my mechanic and 4-5 days time. My mechanic here is always so busy and when I’m down for an annual it’s usually a couple months while he’s fitting me in his schedule.