Do the valve cover, and the rear cam plug O-Ring. Then put in some "High Mileage" engine oil and see how it goes.

 

This particular engine uses a cam PLUG rather than the O ring that is used in the newer Montero/ Montero Sports. It is advised that you do both the valve cover gaskets AND the cam plugs at the same time since much of the job overlaps. Once the valve covers are off, the plugs are a piece of cake - though you'll be doing much of it by feel. Start there 1st to eliminate the smoke effect- then progress to the other leaks as time/money allows. I never recommend using Stop Leak on anything!

J

 

The "high mileage" oil ( like valvoline) is a bit thicker than other oils and does have some additives (in safe levels) which may help reduce your oil leakage rate. There is no worthwhile oil stop leak in a bottle.