I don't replace a seal unless it's leaking. On my '78, I replaced one years ago when I renovated the bike. To this day, I'm still running with one original and one new replacement. Sometimes minor leaks are simply dirt in the seal. Clean it out and many times that will fix it. That being said, it's a good idea to take the forks apart just to thoroughly clean them. Forks don't get hot in operation like a motor so the sludge build-up in the bottom doesn't get broken free, mixed with the oil, and drained out. You literally have to scrub the insides clean, swab them out to get all the gunk out.
You can buy a nice little Allen socket for disassembling the forks. It's a 17mm Allen socket made for VW drain bolts. Jetmechmarty recently talked about this. He bought a Snap-On but there are cheaper ones available .....
https://www.amazon.com/dp/B003LIX22G?psc=1&ref=ppx_yo2_dt_b_product_details
The key to this working is it's small diameter, small enough to fit down inside the fork tube. I have a rather large 1/2" drive 17mm Allen socket that doesn't work. It's O.D. is too big to fit into the fork.