Well, thats your call. It doesnt really hurt anything by leaking, it just makes a mess on your driveway. Maybe if it leaks really bad it could get on your brakes and reduce braking. Or if you let it go too long you could run low on gear oil in the diff. Or it could cause accelerated wear on the bearings and birfield by mixing gear oil with grease.

Redoing it is not that expensive and not that difficult. It is just time consuming and very messy. One positive about doing it is, that it will familiarize you with the front end of the truck. If you do any wheeling and break something in there, it will be 100 times easier for you to do the repair on the trail if you have torn it down before. Plus its a good time to inspect things like wheel bearings and kingpin bearings. Worn out kingpin bearings can cause irregular tire wear, loose or worn out wheel bearings can also create irregular tire wear, as well as many other bad situations.

So yea, if you havent torn into your front end before, go ahead and do it now. Make sure you buy Marlin's heavy duty front axle seals.