If the thing has been setting for a long time the leather seals will start to shrink. If the pump holds pressure and stops without cycling it should be fine ,but keep the new seals on hand just in case. Best case would be to change before the season starts so you won’t get caught not finishing a project on time when promised.
As far as Spray Tips an 80/50 tip will work fine. If using sand the tip should be changed every 4-5,000 gal sprayed. This will ensure you don’t use to much sealer. Tips are 4-8 dollars.