I'm Lucy, and I'd be happy to answer your questions today. I'm sorry to hear that this happened.
When you hire someone to perform a service, there's an implied warranty that they will perform the service correctly. What that means is, if they forgot to replace your oil (or forgot to replace the cap so it all drained out), they're liable for the cost of replacing your engine, plus a refund of the $25 you paid them. They do not have to pay to purchase the truck unless you can show that the cost of the repairs would exceed the value of the vehicle.
You do not have to let them replace the engine (and if they're an oil change place, they shouldn't be offering), but if you take the vehicle back to let them inspect it, that might help you negotiate a resolution with them directly, which could save you the time of going to court. Small claims court takes a few weeks, so if you can work things out on your own, you might get a working truck back faster. In court, it's usually best to have a few estimates of the costs of repairs so the judge can see what repairs were needed and that the amount of money you're asking for is reasonable.
If the cost of replacing the engine is less than $5,000, you can bring suit in Small Claims Court, which is very user friendly and does not require a lawyer. For more than that, you'd have to file in the Superior Court. You're allowed to also ask for reimbursement of your filing fees if you can't work something out and have to sue, but would not get legal fees for this type of case.
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