I'll disagree with jt351...I've had several higher mileage vehicles come through the shop that would shudder and lag that a flush completely solved the problem. Flushing out old crud than can be clogging the ports and inlets for $80 is a lot better than the cost to drop a tranny and rebuild. It's a good first shot for cheap, always start with the easiest and least expensive fix first! A shop is going to charge at least an hour labor to start to diagnose an issue like this, at a minimum of $75 an hour.