1995 Chevy Blazer 4.3L Vortec 4WD is misfiring and can't find a solution?

Well I went to Autozone and had the scan done. They said it's misfiring and that I should replace the Plugs and Wires. I did all the plugs and wires and yet the Blazer still idle and acted as though it was going to stall. When driven I get hardly any acceleration and it chugs along. So me and dad changed the Rotor on the distributor cap. Still the same issue... The service engine soon light is flashing away and When we changed the rotor we looked at the posts on the dist. cap and they seemed to look fairly okay. Meaning there was hardly any corosion on them. When the truck is started and turned off you can smell gas and I went under neath the truck to find that i'm getting oil leakage somewhere. Looks to be where the exaust and Cat meet. (Guess) Well when dad runs out of answers and i'm still scratching my head....Where to go from there??? Were tight on money right now and can't really afford a $1000 Repair job.... He told me to get the Distributer cap replaced and see if it helps any. I have high doubts that it will.... WHAT DO WE DO?!?!?!