Ok, not knowing anything, this is what I would do - and some I'd do myself, and some the dealer. My philosophy is I don't want to deal with any of these things during the riding season since winters in NE Ohio are pretty nasty - so maybe I go overboard on potential problems that can easily be prevented. A good bit of this list I would let wait for winter lay up. Your bike has 50K miles on it (not a lot for an ST) and is 14 years old.
In no particular order:
Check date code on tires - replace if more than 5 yrs old or if tread is thin. I never go all the way down to the wear bars because a car i had hydroplaned - not a good feeling in a car, let alone a bike.
Check brake pads. I'd replace them if they are significantly worn. Check secondary master cylinder
Change all fluids - brake, clutch, anti freeze, final drive, oil and oil filter.
Check for anti freeze leaks. Check hoses for deterioration.
Check the battery. (maybe replace)
Check front forks (change oil), check rear shock, rebuiild preload adjuster. Somebody said recently that the shock is good for 40 to 50K miles. I'd do more research on this and maybe redo the front and rear shocks. Check steering head for play. (If the bike rides well, I would leave all shock work for winter - depends how far you plan to ride it this summer).
Check wheel bearings.
Check valve clearances. While I'm in there, I'd probably replace the spark plugs or at least check them.
I think your bike has carbs - I'd probably balance them and check the 5 way T below them as mentioned elsewhere on this site - I know nothing about it now but it can be a maintenance issue.
Change the air filter - or at least examine the old one and decide.
I'd also check the electrical system for ahhhhhhh, inexpert tinkering by previous owners. And correct anything that I found that was egregiously wrong.
Don't know about timing belts on your bike - I'd have to do research to see if there is a time limit on the belt - you haven't hit the mileage mark for this yet.
And you have a whole new world of farkles to explore.
Doubtless other guys here will tell me I'm all wet on this list. Did I forget anything? As they say, ymmv....