Vac testing really helps with determining if you have a bad crank seal. It will help you figure out if you have a bad impulse line and/or intake boot. If you dont have the stuff to do it, its just cheaper to buy lines for single saw. (Plus if they are bad, you gotta buy em anyway....) Clean the air filter with just soap and water, let air dry. DONT try to clean the fuel filter, just buy a new one.
If you havent been into your carb before, you might have to put a kit into it, but they can be had for less than $10, and its not too hard to do, honest.
The spark arrestor will be in your muffler outlet, if you still have one. Should be held in with a single screw, and you can pull it out and burn it off with a propane torch. One of the things that you dont need to replace