Montenido: These are not stupid questions. I had my first sea trial this season. Let the owner take it from the dock and back to the dock. Other than that, it is on you to put her throught the test. You should hoist the sails, let the owner steer temporarilly. When the owner is at the helm, inspect the engine while under power. If the boat has cockpit access to the engine, take the cover off and watch the engine at idle, and at incremental RPMs up to full power. Don't forget reverse. Listen for vibrations. Make sure you aren't getting black or white smoke from the exhaust and that enough water is exiting with the exhaust. When you are at the helm, try to feel what you can. You really want to sail her hard if you have enough wind. Once you are back at the dock and you sign the dotted line, it is your boat. Don't be shy about raising issues that the survey highlights. The owner wants to sell you this boat and should/will make some concessions. Best of luck to you!