I think my oil seal is failing on my left fork and needs replacing.  Has anyone here done something like that and do you think it's worth the hassle?

Worth the hassle?  If you don't replace it, your suspension will get weird, your brake pads will get soaked with fork oil, and you will die suddenly when can't stop for something important.  It is not that hard to do yourself if you have a manual and a 1.5" diameter piece of PVC pipe to use as a seal driver.  Otherwise pay somebody to do it.  You might want to do them both.  Good excuse to change that nasty old fork oil anyway.

not too tough, just remeber what goes where and have some time set aside.  did mine last weekend w/o a manual.  toughest parts were getting the triples/headlight off and on and somewhat difficult to get the bolt at the bottom of the bolt out (hint:  impact gun and a couple extra hands work wonders).

Getting the triples and headlight off?  yuck.   I just supported the front, loosened the clamps, and slid the forks out, leaving the clamps haeadlight and all that stuff where it is.  Another nice touch; break loose (but don't remove) the damping rod bolt in the bottom BEFORE you remove the fender/fork brace, and loosen the tube caps a tinch too.   Then it all comes apart nice and easy.  Still an oily mess though.

Oh yes, I definitely plan to replace it, I was just wondering if it was worth the hassle to do it myself or would you guys have paid somebody to do it.
I've been thinking of swapping the springs out for progressive springs, maybe I'll kill two birds with one stone.

it can get pretty expensive to have someone do it.  i think there was a quote someone got on the board in another thread.  not too many parts, just remeber which way they go in.  if you do it yourself, make sure to put the upper leg in before you put the metal slide.  it's not fun to get out and the upper wont go in if the slide is already in.

I paid just under $200 out the door (parts, labor, tax, etc) to have both seals replaced last week.  Its something I would have liked to have tried myself but with so little wrenching experience I'd have preferred to have a more mechanically inclined buddy help me and he was out of the country on business.

I'd say that was a pretty darn good price considering the original estimate was for about $275 but if you're confident you can do it yourself you can save $160+ in labor.

-Neuling
Oh yeah, and while I was at it I bought some progressive springs (an additional $75) and had them use 15w fork oil, both based on the consensus on this site.

If they've not been moved before, and you don't have acess to power tools, the damper rod retaining bolts at the bottom of the legs might defeat you.  If you get this far and get stuck, you can still take it to a shop, and save yourself a heap of expensive labour by doing the dismantling and re-installation yourself.

When you are working on the fork legs, it is very important that you keep the sliding portion safe from scratches and gouges.  Marks like this in the chrome will quickly chew up the lips on the new seals.

When you have the forks off, think about installing fork 'gaitors' or 'boots' to keep road muck and grit off the fork sliders.  They cost a fraction of the price of a new sets of seals, and your seals will last much, much longer.  When re-installing, clamp the legs to the correct torque to prevent distortion of the tubes.