Basic 2-strokes are easy enough to work on compared to some of the modern 4-strokes that get hooked up to a laptop for diagnostic report.
Annual servicing should include impeller change, lube grease points, renew spark plugs, drain and clean fuel bulb on outboard (also worth investing in external fuel filter), change gear oil, grease splined prop-shaft and drive shaft, check all electrics and renew terminals where necessary, check idle speed, check torque of flywheel nut, check thermostat and clean housing (you'll need to renew gasket). Invest in a multimeter - they're cheap but invaluable when it comes to electrics, checking battery condition, etc. good luck.
If the 5hp is 2 stroke and manual start, ignore thermostat, but renew starter recoil rope and drain fuel if it has integral fuel tank.
In my experience - always best to run engines dry of fuel prior to storage/winterisation to avoid carb issues.