I think He is talking about the front pan seal where the timing cover meets the pan....If so, I would blast it good with brake Cleaner and run a bead of silicone over it then smooth it with my finger....shit I do that with it while it's on the engine stand...never had one leak yet....knock on wood. It is a pain to replace the gasket in the car but I've done it...either got to get the pan loose or pull the dowel pins from the front of the block to get the cover off...if you have a chrome timing chain cover that's probably why it leaked...wire brush the chrome off or rough it up if that is the case.
If you are talking about the seal in the center of the cover where the balancer goes that one would be easy to change...but I've never had one leak. Is the balancer rusty or rough where the seal rides? Are you sure the balancer is all the way back onto the crank?