When I bought my boat I was given a receipt for servicing the outboard. This had been done a few months earlier and included an item "to check and rectify cooling". I serviced the engine and discovered no vanes on the impellor and water channels completely choked up with barnacles. No way had that job been done.....but they had charged for it.
Some dealers may do a good job, but many don't.
Spend the money on a manual for the engine and some tools.