Welcome to BF, Jawnee!

I always say, "Hey! If it ain't broke, don't fix it!"

If the time comes that you need a new fork, then get a rigid fork, unless you're satisfied with the fork you have now. In that case, just get a replacement suspended fork. If you need new tires, then just get new tires. That Marin Stinson is a nice riding bike!

Just take it to the friendliest bike shop and have them give it a tune up. That's it! That's all you need to do!

Good Luck!