If I miss anything please fill in the blanks and if someone feels like moving this or sticky it go ahead if you think it is worth it. I hope this helps. I would say this is a very simple job a newbie could do with simple tools and common sense. This was all done on a 1999 camry 5S-FE auto. I always thought the 3S-FE also had threads on both end of the tubes. I didn't think they were pressed it.
I would go to the dealer and get all the parts that is what I did. It didn't cost that much. The dealer here offers 10 percent off if you have over 100,000 on the car. I got new plugs, wires, tube seals, and thread sealant. I can't remember but I think I reused the valve cover seal.
1. Disconnect the battery, it is for your safety, remove the negitive. I highly recommend taking the hood off, It sounds like a pain but it is very easy and I do for most of the more involved work. And the way this engine lays back. If you don't you will have a sore back leaning under the hood, but to each there own.
2. Take the spark plug boots off. I left the spark plugs in the whole time to keep anything from falling into the cylinder and threads.
3. Loosen the spark plug tube nuts. These are the large nut under to spark plug boot. And take the tube seal off, it is under the nut.
4. Carefully take the valve cover off. A rubber mallet might help, hit the side of the valve cover to knock it free. I've learned in the past that the design of the rubber valve cover gasket is superior and usually will not leak if reused. But do as you see fit.
5. I did this a while ago, but I think I just used a channel lock or pipe wrench to remove the tube. Just grab it on the middle outer section and turn it out. It might be a good idea to sharpie the number on the side to put them back in the some cylinder.
6. Clean the old sealant off the tubes. I used a wire wheel on a bench grinder to clean out the threads.
7. Put new sealant on, follow directions on tube. Thread into head.
8. I put a nut on the tube. I held the tube with a pipe wrench and tightened the nut about 5-8 foot pounds more than the final tube nut torque when every thing is done. Then I used a large socket on a torque wrench to tighten the tubes in a few foot pounds more than the final torque on the tube nuts. Remember this is a steel tube going into an aluminum head. The sealant should do most of the sealing, not the tightness of the tube. It just needs to be tighter than the nut will be so it will never want to spin when you install and remove the nuts when the valve cover is on. Once the tube was in place, I put the pipe wrench on the tube and took the nut off. Once all four are done then put the valve cover on.
9. Clean off the valve cover seal if reusing, and clean off the matting surface of the head. You might want to put a small drop of oil and the four corners where the flat part of the head goes to the half round where the cam sticks through. Then put a little black RTV sealant at each of these points. Then put the valve cover on. The oil will keep the RTV from fully sticking to the head the next time the valve cover is removed. Also if the valve cover seal is going to leak it would be at this point. I had a new one leak on a tercel and I had to do this trick.
10. Put the new tube seal over the tubes.
11. Put the tube nuts on and torque to the listed spec. in manual.
12. Put new spark plugs in if you choose, and new wires on.
13. Reinstall hood.
Now that wasn't so hard! Just a little time consuming