The way your removing the hubs is the hardest in terms of weight.
When I replaced a seal on the drive axle I did not remove the tires seperatly. I simply pulled the axle and then jacked the rear end housing so the tires were right at the point of leaving the ground, then just slid everything off on a smooth slippery piece of metal. I usually get stuck with no help and by doing it this way I had to lift nothing.
Removing it as you are with the brake drum still attatched to the hub makes for a very heavy assembly.
Here, once again, prevo adds another step to a process that in most other cases does not exzist. The brake drums are screwed to the hubs with large flat head tapered screws. I might add that they are also not easy to loosten and or remove. I'll bet you tried but couldn't.
It will not be easy for you to reinstall with the new seal with the drum still attatched to the hub. To be safe you might get some help lifting that back up so as not to nick that new seal going back in. Either that or get those tapered flat head screws loose and out and seperate the drum from the hub.
OOPS, sorry, better late than never.