If you have a blown head gasket or a cracked head you will get rough idle when you first start the truck. Additionally you will probably have problems with fouling the same plug/s on a consistent basis. A cracked head or blown gasket usually won't have any externally visible leaks. If the head gasket is leaking externally it would most likely be coolant if anything.
If your truck has overheated recently than it's very likely that you have a cracked head or head gasket.
Ways to check for a blown head gasket/cracked head:
1. Slowly loosing coolant.
2. Smoke at start up.
3. Rough Idle.
4. Fouling spark plugs on a regular basis.
5. Inspect the block for coolant leaks around the heads, and pull the spark plugs after they have been sitting for a while to inspect for coolant.
6. Check for coolant for presence of oil.
7. Send your oil off for a used oil analysis. If it comes back with coolant contamination it's most likely a head/gasket.
A blown valve cover gasket will leak oil all over the place, but should have nothing to do with coolant. It should be obvious if it's leaking from the valve cover. You will have lots of white smoke, and your oil level will consistently drop over time.
If you do end up tearing down the motor it would be a bad idea to just replace the head gasket. You will want to take the cylinder heads to a machine shop to have them magnifluxed to check for cracks and machined back into spec so they will go back on correctly without creating any new leaks. If you do not take the cylinder heads to a machine shop you run a very high risk of having to tear apart the motor again.
You're probably looking at $100 in labor to check for cracks and machine the heads flat. If the head is cracked they can repair them, but it's probably a better idea to get an aftermarket cylinder head from places like Alabama Cylinder Head or Ideal Cylinder Heads, or your local junk yard.
You will need to spend about $150 in gaskets alone. You will need to replace the intake gaskets, valve cover gaskets, head gaskets, and more. You will also have to replace the head bolts ($45)
You would be lucky if it's just a blown gasket. If that's the case you can probably get out of this for under $400 if you do it yourself. If it's a cracked head you're looking at around $600-$800. That cost quote will of course depend on if it's just one head or both heads that are cracked, and if you choose to repair or replace the heads.
If you take it to a shop you're looking at at least getting charged for 9-10 hours of shop labor to tear apart the motor which at $80 per hour rate is $720 minimum in just labor alone. Then you'll have to factor in parts cost, and machine shop charges. I would estimate that after it's all said and done you're looking at anywhere between $1500-$2500 depending on the shop you choose.
If you have some buddies who are mechanically inclined, can track down all the parts you are going to need, have access to an air compressor with an impact wrench and die grinder, quality torque wrench, and a breaker bar, and can afford to be without a car for 7-10 days you will save some SERIOUS cash, and learn a lot about working on cars.
If it's a cracked valve cover, or valve cover gasket than this would be a fairly simple repair in an afternoon and should cost less than $100 to fix. All that's required to fix that is to pull the upper intake, injector manifold, and lower intake. After that you would need to remove the valve cover and grind the gasket material off cylinder heads/valve cover with an angle grinder and a red 3M "Raylock" pad. Then apply the new gasket with RTV Black Silicone and reassemble in the reverse order.
If it makes any difference just about a year ago I was just learning how to change my own oil. I had all the symptoms that I listed above and used the forums to self diagnose the problem as a cracked head or blown head gasket. I learned SOOOOOOO much about my truck, and cars in general (I still can't change the wiper blade). It's not hard if you just take your time and mark everything as you go. As long as you mark where every hose, cable, and wire connects when you are taking it apart you will be just fine. Just make good use of your digital camera and take pictures at every single step. With a digital camera, a Haynes shop manual, and the forums, you should be able to fix this yourself. It's easier than you think.
Edit: It's going to be almost impossible to diagnose your situation from a blurry picture of used motoroil on a paper towel. If you really want to know whats going on, invest in a used oil analysis. These guys are pretty well known http://www.blackstone-labs.com/?gcli...FQmdnAodCldHrQ