As a Smog Check Tech in California... I can offer you this information:
The fact that the smog technician at the test only station could not hold your vehicle's speed constant may be responsible for your vehicle's failure. It is very important to put your vehicle under as little stress as possible during the smog test. Varying the vehicle's speed up and down during the test will change fuel delivery and potentially cause high CO... as we see in this case here.
Your vehicle's oxygen sensor should be able to determine the correct amount of fuel to deliver the combustion chambers based on the oxygen content. Assuming your vehicle's oxygen sensor is not defective I would recommend having the vehicle retested, hopefully at a constant speed.
If this doesn't work i would then recommend having a smog check repair center conduct a "feedback test". This test will insure the oxygen sensor is in proper fuel control.
I hope this information is helpful. I recommend visiting http://www.smogtips.com (these are the folks I work for) to get more answers or to email one of our smog techs personally.
I gave you the California site earlier but that the seller is required to provide the buyer with a valid smog inspection certification at the time of the sale or transfer.
Smog certifications are good for 90 days from the date of issuance.
Yes, CA does require smog checks.
Head Gasket Blown, burning up throw the exhaust!
It depends on how busy the shop is, how many people work there, and what repair you're needing. In a very busy 1-2 person shop it can take 2-3 days to look at a vehicle. If you needed an estimate that requires extensive time to disassemble, they may want to wait until they are sure they won't need the bay and lift while they are checking it. Most garages don't charge for estimates (nor should they in my opinion) so they give priority to paying jobs. If it is a large shop and/or a simple repair issue then find another place to have it worked on.
the 3.4 engine should last quite awhile, adding lucas oil stabilizer in your engine should help it last. How much you use is up to you, its a little expensive to use 70% of that stuff in your engine every oil change. Plugs and wires. fuel filter. Drop the pan and change the filter in the transmission, without skimping on good trans fluid to fill it back up, possibly another bottle of lucas transmission slime. Make sure valve cover gaskets, oil pan,..ect. doesn't leak. Make sure coolant is of good quality. coolant should be changed every three years. CV axles can be changed out, but if they don't click theres no reason. The u-joints in all your driveline shafts can be swapped out. double check ball joints, tie-rod ends, bearings, sway bar links, shocks, and if your springs sag.(all can be changed when they are noticeably bad) At 200,000 everything is past due, if you start to feel like the engine is starting to head south, don't neglect the truck. a cheap junkyard motor or even trans always does the trick. If treated right that motor could reach well over 300,000