He is right, the cams will do that, especially the pass side. It's happened to me more than once with no ill effects. I can't remember if the cam has a hex section on it (my other car does) to hold it, but in order to remove the valve covers a lot of other components must be removed. I didn't do this and it's not necessary IMO. You can't use the cam gear nuts to hold the cams because you need to remove the gears to replace the seals. The second time I replaced my TB, I just gently allowed the cams to rest where they wanted to using a wrench on the gear nut to guide them and prevent them from snapping round. Then I removed the cam gears. The pass side cam (if I remember rightly) really sits on a knife edge, in terms of wanting to snap back, when you line up the timing marks so be ready.

Make sure you get the tension right following the factory procedures. It can be a pain (spells and a wand help <img src="/forums/images/graemlins/lol.gif" alt="" /> ), but it needs to be right for obvious reasons.

Justice's procedure thread for the DOHC is the same on the SOHC, just 2 less cams and a shorter belt <img src="/forums/images/graemlins/smile.gif" alt="" />

If you don't know what was changed last time or ever, I would replace;

TB (Mitsu for me but others have used belts produced by Gates and Conti, I think)
hydraulic tensioner (Mitsu for sure)
tensioner puley (I'm running Dayco. 40k miles later no issues)
idler pulley (same as above)
water pump (Mitsu will last 120k miles, aftermarket I would replace after 60k. I just replace the factory pump each time anyway as it's just not worth the hassle of changing it if it goes before 120k miles)
cam and crank seals
crank bolt (Mitsu. New factory design)
accessory belts and idlers

It's not cheap, but a lot cheaper than a new engine.

I may have forgotten something, but someone will chime in if I have.

You can remove the radiator fan and shroud together without removing the radiator, but having the radiator out the way does give you a bit more room and this would be a good time to have it cleaned if needed. The AC condenser bolts are best got at through the d/s wheel well. I didn't know this the first time I changed my TB and it was a royal pain in the <img src="/forums/images/graemlins/butwiggle.gif" alt="" /> . Later, I lifted the wheel well rubber flap and there they were...doh!

Also, if you are planning on changing the valve guide seals don't think of them as a 'while I'm in there' doing the TB job. The cams do not need to to removed to change the valve guide seals and the job can be done without touching the TB. I learned that the hard way too <img src="/forums/images/graemlins/notooth.gif" alt="" />

Good luck. Take your time and be sure the set the belt tensioner right. It's good to have some other people with 3.5L SOHC engines wrenching on their trucks <img src="/forums/images/graemlins/kewl.gif" alt="" />