i'll be doing the same soon. we have a 200 amp service, but the house was biult in 1875. it origonally had gas lights, then a 60amp service. it has knob and tube, bx, older romex and new stuff too. the main issue is ungrounded outlets and overloaded circuts. some have way to many draws on them, others have one light bulb.
its all complacted by the fact that over the years so much has been changed that its hard to follow lines around in the basement, there are tons of unused wires, wires that lead no where. ive removed a ton so far and have more to remove before i can start rewiring the older part of the house. im lucky to have an unfinished basement and attic, as well as a 2ftx2ft chase in the middle of the house.
for anyone doing this i recommend buying some pex to protect wires form chaffing as you pull them. its a two man job but ive seen i help alot. one man pulls, the other holds the pex and feeds the wire. and buy some glo-rods or similar by greenlee, they help alot