My 4runner has a 22re engine, it sounds like a rocker arm is worn out or loose or broken. I know with rangers that means the engine is going to blow but with full size fords its not a huge deal. Is this something to really worry about?

It is important, but not fatal. Get it fixed or your engine will not run well at all. You are crapping out 1 of 4 cylinders.

It may not be a rocker arm, and it may not be the only problem. You better make sure first before you decide to spend or not spend money on the engine. Do a compression check. Should be ok. If the compression is bad on one cylinder. Then do a blow-down check to find the cause of the bad compression. Evaluate this carefully so you don't spend money on something that is not the major problem.