It's not that bad. Was cool pulling the old weights out of the frames. I had no idea what I was doing when I changed them out but the heat savings was worth it we still do not have insulation in the walls though. Makes a huge difference in the winter.
Replaced mine about 10 years ago. Couple had framing water damage and I had to pull some wallboard to replace rotted boards. Lot quieter, and no more air leaks. That was way too much like work, did about two a day till done.