I was just writing the reply, and then I lost my connection and it looks like my post was never uploaded.
He substituted rebuilt parts for new ones without telling me, raised the price by a quarter at the same time and billed me for several shop mix-ups. (Originally I hired them to inspect the van to see if it was repairable and what parts were needed, but they did a general inspection instead and didn’t get the dimensions/part numbers. When that resulted in ordering the wrong parts and having to re-do a lot of the work, they billed me for it.)
It’s about $1k in labor and $2k in hauling costs due to leaving my van inoperable (which he may not be liable for).
Connecticut law may be an outlier, since in most cases the state seems to require signed change-orders for going over an estimate:
Connecticut law requires that a repair shop obtain your written authorization that provides an estimate of the maximum cost of parts and labor before performing any work which must be signed by you. In fact, a repair shop must get your consent before charging you for an estimate or diagnosis, and your consent must be in writing if the charge for estimate or diagnosis is $50 or more. The repair shop must also keep a written record of the specific repairs you requested or a brief description of the problem that requires repair.
Exceptions to this general rule include:
After hours: If you leave your vehicle at the repair shop at a time when the shop is not open for business, the estimate of the cost of parts and labor and your authorization to do the work may be given verbally when the shop is open but still need to be recorded on your invoice.
Unknown problem: Sometimes a repair technician will not know the cause or extent of a problem until after your vehicle is examined. In this case, the shop cannot give a complete written estimate until the problem is diagnosed. Once the shop learns what repairs may be needed, the shop must notify you, give you an estimate of the maximum cost for parts and labor and obtain your consent before making repairs. If consent is given verbally, the shop must keep a written record of your approval.
Consent: You may agree that the repair shop does not have to give you a written estimate. This is called a waiver and is only allowed if it is in writing, signed by you and sets a maximum dollar amount for the repair work.