Is my car going to break down?

I have a Saturn Sw2 1996 4-cyl and recently when i started it after work i was shaking horribly as if it was going to stall. I shut it down waited then started it back up and it had the service engine light on but wasn't shaking. I have replaced the spark plugs and after going over a bump the light turned off. Now today as I accelerated to go onto the hwy the light came back on and the acceleration feels like it's not working all that well. However it hasn't shaken like that first day. I have already bought a fuel filter and am going to replace that but I would like to know where the fuel filter is located as well as if this is the problem.