I would try to find the most reputable dealer in your area that has a good service department who sells your hot tub brand and regularly services them. get to know them and they will see the value of you as a customer when you buy chemicals from them or need service in the future. contact the service manager there and ask his advice. maybe they will perform a check-up for some reasonable price.
That said here's what I would do in your situation. barring any evidence of damage I would simply hook it up, fill it and bring the water to within ballpark balance (you won't be getting in right away), and let it sit for 24 hours before you heat it up (or set to a low temp). sanitize as you would normally, or even a moderate shock. note very carefully the water line and the condition of the filters and everything in the equipment compartment. run the jets, operate the air injection valves. make sure everything works. make sure the heater works, although at this stage it will be a waste to heat it to target temp. inspect for leaks everywhere such as around the perimeter, inside the equipment compartment. etc.
depending on your level of confidence, you could extend the "burn in" test longer. watch the water line for leaks, accounting for some evaporation of course. keep operating everything and looking for leaks.
When you are satisfied that everything is operational and there are no leaks, then purge the spa with the EPA registered product known by the name of ahh-some gel (I'm in the better safe than sorry category). Note that I have no affiliation with this product but I have used and tested it extensively and find it to be very effective. Note too that there are alternate schools of thought about the purge -- some argue that it is not necessary; I only recommend the purge here because I have personally experienced rapid biofilm growth in a brand new, never-been-used spa over a two week period, so I feel it is even more important in a used spa. Anyway, if you're down with the purge, just follow the label directions. Dose your water, run the jets, etc. if you don't see very much material released by the purge then you're done. drain, wipe down, and then refill for use. if the ahh-some purge releases a lot of gunk, then drain, refill, and purge again.