Get your quote in writing.
Nothing like getting a price from a car repair shop, agreeing to let them do the work for said price, requesting that they do nothing else without checking with you first, and then receiving a voicemail message two hours later from the manager saying that the price is going from $5xx to $7xx because he forgot to add something during the quote and there is "no choice."
To sum up my experience in a word: Sad!