snunicycler

first of all. hi, i'm mitchell.

ok, i have a v8 silverado that is throwing a CEL for a cylinder misfire on cylinder 3. so far i have replaced the spark plugs, spark plug wires, distributor cap, and rotor under the d-cap. the CEL is still on and it idles kind of rough. still drives fine and starts fine and everything. not sure what else to try.
when i am idling the RPMs go down to about 600.

any ideas as to what could be the culprit? the haynes manual mentions possibly the vacuum leaks at the intake manifold or maybe a dirty/clogged fuel injector. i am a do-it-myself kind of guy but i dont really have access to a whole lot of tools. and i have only really done basic repairs (the hardest thing i have done is replace a starter on a neon... in the snow) are these easy things to check/diagnose/fix? or should i be taking it to a mechanic at this point?

also, this might not be related at all but just in case it is, i had a oil change about a week before the CEL came on (though i doubt it is related).

thanks guys!