My 2000 Chevy S10 shakes alot while idling, and the check engine light is on and blinking. I think it might be the fuel injector, I changed the wires and spark plugs but it's still doing it. And oil or fuel seems to be leaking onto the sparkplugs

Check the vacuum line under and in front of the throttle body...with engine idling. It is located under where the air filter snorkel attaches to the engine. Then check all vacuum lines at the intake manifold. Check vacuum lines at distribution block on firewall and check the large brake booster vacuum line from one end to the other. You'll find it!

The age of your vehicle guarantee's a vacuum leak. It may sound silly but the truth is rubber grommets and hose's shrink and dry out over time and the harsh environment under the hood makes it worse. Check all vacuum lines and fittings attached to the intake manifold, valve covers(pcv valve), and be sure to check for a vacuum fitting on top of the intake just behind the throttle body. Does it fit tight in the hole? You can seal loose fittings with a high-temp RTV (Red) silicone sealant/adhesive. Several small leaks add up and your engine, heat/AC, will be all to glad to tell you about it.