I have a 96 chevy suburban 4x4 454 and i want to know why the motor is still shaking?

I have changed all the spark plugs and all the spark plug wires and it still shakes. It started 2 Days ago...I was on the highway and it started shaking just a little and when i got to a stop i felt the truck shake. When i got home it started shaking even more and it smelled like gas. Please help I am a beginer at mechanics, I am fixing my truck from what i see on youtube and the stuff i read. I just cannot find any other info on the truck any advise would be greatly appreciated. The truck has 172,000 miles if this helps. I was thinking of changing the roter abd roter cap to see if that was it. If any one has a video or can guide me thanks.