I recently replaced the three front seals. To install them, it is easier to have a piece of pipe to help drive them in straight, especially the crank seal. When I say "drive them in" it is really lights taps with your had or a mallet. Check the FAQ. The Hanes book has all the retorques for the gear bolts, or check back here.
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Tom F

Sure, it CAN. I just did this in one of mine. You need to get the cam pulley off, of course, so you've got to break loose the nut on it- usually a couple whacks on a wrench will break it loose or you can block the timing belt from turning with something.
To get the seal out, you'll need a pick or something sharp, or a tiny screwdriver. It wants to pop in an disappear, but you've got to be patient and hook it and pull it back out. Once it's a little sideways, it'll come right out.
Of course, it's not that hard to replace the valve cover gasket either... and it's cheap so it may be easier to just do it the "right" way.
Good luck!
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Rob Bareiss, New London CT ::: '86 244DL- 215K, 87 244DL- 230K, 88 744GLE- 198K, 91 244 180K

The valve cover does NOT need to come off but you will need to remove the timing belt & cover to get at it. I usually use a strong curved pick to pull it out, just be careful that you do not scratch the cam sealing surface. I suggest you replace all 3 front seals while you are in there, it only takes a few extra minutes and costs a few bucks more.
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Bob Kraushaar '94 945T, '91 940T(back from retirement), '88 240, '84 242T, '94 F-150, '89 560 SL, '68 Shelby GT-500 KR