on top of the valve cover (usually...couple exceptions...dunno what kind of car you have). you'll find it between the #2 and #3 plug tubes.

it looks like a piece of hard plastic tubing bent 90 degrees about halfway along its length.

some cars have it coming out of a box the size of a juicebox closer to the firewall. you'll know it when you see it.

it's very easy to replace, do it yourself. the part is only like $15-20 depending on your car.

it's amazing how easy this fix is...and how many nasty problems a broken pcv can cause. high pressure can do nasty things to oil seals.