I took a series of pictures of this job on my 2003.
I removed the winshield wiper cowl....the black part that is in between the windshield and the hood.
Removing the upper intake manifold requires you to have a 8mm HEX bit, so make sure you have that before you start, to save a run to the store to buy one.
There are COOLANT lines that connect to the throttle body, so you might want to drain a little coolant from the drain on the radiator, passenger side back side.
Be prepared for some coolant to drip as you work with the coolant lines on the throttle body.
The upper intake manifold is supported at the REAR, my pictures show where the bolts are, and the sizes of them (yes, there is more than 1 size bolt to remove back there)
I replaced the upper intake manifold gasket, don't know if it was necessary, but I did.
I also replaced the spark plug tube seals (part of the Felpro valve cover gasket set that I bought).
I would strongly recommend that one replace the FRONT valve cover gasket FIRST so that you know that part of the job before you have everything apart and are trying to lean back and see what you are doing with the back.
I did the front and back on separate days.
For spark plugs, use the spark plug that TOYOTA lists for YOUR year, different years use different plugs (within 1st generation with the same 1MZFE motor).
They should list a DENSO and a NGK number in your owner's manual, use either one.
You do NOT adjust the gap on the spark plugs.
Here is a link to the first in the series of pictures for the front valve cover gasket
http://rides.webshots.com/photo/2609915850011220610XGbmsa
Here is a link to the first in the series of pictures for the cowl.
http://rides.webshots.com/photo/2862435300011220610zdMJTk
Here is a link to the first in the series of pictures for the upper intake manifold, followed by the rear valve cover gasket.
http://rides.webshots.com/photo/2168308870011220610QVNRpZ