How do you replace valve cover gaskets on a 1989 F350 5.8L V8 EFI?

Remove valve covers. (Be careful not to drop bolts where the sun doesn't shine)

After removing bolts you may need to pop valve cover off cylinder head with flat screwdriver.

Clean off any old gasket or sealing material off cylinder head where valve cover gasket mates to cylinder head. Make sure dirt does not go onto cylinder head area by valves, you do not want junk going into your oil! Use paper towels, rages, whatever you need to keep dirt off top of cylinder head. You can use flat screwdriver, wire brush, die grinder (with gentle grinding head), or anything else that will scrape the material off cylinder head.

Spray brake cleaner (or equivalent) onto a clean rag/paper towel and ensure mating surface (area where gasket meets cylinder head) is perfectly clean.

Install new gasket parts into valve covers (it will not hurt to first give valve covers a quick cleaning with brake cleaner).

Apply black silicone (or equivalent) to cylinder head where valve cover gasket mates.

Install valve cover (with new gaskets in place on it).

Use socket with extension to tighten bolts (no socket wrench attached) hand tight only, you may tighten bolts in any order. Also ensure threads on bolts are clean ( somewhat clean if you are lazy).

Torque specs should be included with new gaskets.

Properly torque bolts in sequence.

If you do not have torque wrench or you are not familiar with how to properly torque a bolt in sequence, don't worry: it is very easy (for this particular job)!

For this application just tighten bolts as tight as you can as if you were using a screwdriver with no leverage. Tighten bolts in center first and work your way out to sides of valve cover.

If you do not do it perfect, don't worry, you have a 95%+ chance of doing it right if you understand my instructions.

Now that it is the winter season, it would not hurt to allow a little extra time for the silicone to dry, because the temperature slows it down, if it is summer- be fairly quick to assemble because silicone will dry fast. If you do the job in summer, and you have some type of problem- make sure silicone is still "tacky" before installing. If it isn't, you must clean all silicone off and start over.

Also read the precautions on brake cleaner- it does not do good things for lab rats in California, so work in a well ventilated area!