A friend needs some tune up help

[bn37]

Hello everyone and thanks for this forum! I'm trying to help a friend get his boat ready for the lake. The engine is a Mercury Black Max 150. I don't know much about boats, but I've worked on tons of cars, trucks, and small engines. The boat has been sitting for a couple years so I'm guessing the fuel needs to be drained out of the tank and carbs. The plugs were changed a year or so before he parked it, but maybe they need changed too. I'm thinking the trailer at least needs the hubs lubed. I'm not sure what else to do. I'd appreciate any advice. Thanks!