First of all, you want to get that filler plug in the side of your tranny loose before you drain it. If it is frozen, you have no way of refilling it. I imagine you have the ZF tranny which is quite different than the one shown above. the filler plug is very close to the CAT so be careful as it is very easy to burn your hand when refilling the tranny with the hand pump. There is no other way to fill the tranny. And Yes, My motor was running when I filled it. You may find that the pan bolts are frozen in place. I had to heat my pan bolts with a small torch and jar them free with a small drift. I destroyed three brand new torx bits trying to get them out. After this process, you will need new bolts and washers. I replaced my bolts with tempered steel hex heads. I also used anti -seize compound on the new bolts, so next time is a breeze.

Good luck