I just received a 9.9 hp Force outboard motor. It's about 15 years old but has no more than 10 hours (all saltwater) on it.

It's been sitting in a garage (salt air) unused since 2001.

My question is do you think it would hurt anything to try to fire it up as is, or do I need to get it lubed/tuned up first?

I would take it first for an inspection.

x2 on getting it checked out.

Assuming it looks good, after that long sitting still, change the oil, lube it up good, check the plugs and everything and then try to fire it up.

I would not start it without checking out the impeller and cleaning out the carb first. The impeller provides the water to cool the engine. Don't risk it not pumping water. It only cost $10-15. Change the lube in the lower end.  Look for any water mixed in. If you see that the lube is a milky color then replace the oil seals in the lower end. A carb gasket kit...maybe another $10. Clean the plugs. Squirt a couple of hits of Marvel Mystery oil into the cylinders to lube up the rings real good a few days before you start it. Let the oil soak into them to make sure they are free. Clean the plugs.....nah, just get some new ones...couple bucks each, ground them to the motor and see if you see any spark when slowly pulling the start rope. If you do then your in business. If you use any starting fluid, make sure it has some top oil lube built in. Mix a can of Sea Foam in with the gas/oil. Let us know what happens.

I just did this to an old $50  9.8hp Mercury I came across that had not been cranked in longer time than yours.  Ran like a top.  I have had the motor out three times now fishing with no problems.