Primary cover is not very hard to remove. Drain the oil, loosen the chain adjuster under the primary, remove the bolts and shifter. Pull the primary cover. Fix the pin, or punch out. Reinstall the cover in reverse order, remembering to pull the chain inspection nut, and adjust the chain tension to spec. Nothing in there to spring out and fly across the room, just a oily mess to have to clean. To put on a bench, you will have to remove the clutch cable, and it is pretty easy, once you see it in the cover. If you remove the cable, you will have to readjust to get the clutch to work properly. Usually just cable adjustment, unless your clutch needed adjustment to start with.
If that is to complicated, you could always redrill the peg mount in another spot, and match the hole up to the cover and install a new pin there.
Definitely just pull it and repair it on the bench. Removal and re-installation is a pretty straight-forward procedure, which has already been described. You will find the removal & re-installation to not be very time-consuming or difficult.
The weld is as hard as it will ever be, so yes, drill it. I always run a half dull file around the gasket mating surfaces, to make sure everything is flat. Not file it, but just a easy smoothing, and remove any jagged edges or humps, but be careful, you can do more damage than good. Keep the file flat and little pressure. Use a new gasket and some good gasket goo, (not silicone, but some good permatex brand gasketmaker) I do both sides, since I always replace the gasket when I take them off. Harder to remove and clean up, but makes for less leaks.