From the standpoint of liability, I wouldn't merely change out a 33 year old breaker panel without bringing the rest of the service up to current code standards. You didn't mention what size your current service was but if you intend to replace a 100 amp service with another 100 amp service you're not adding any value to your house, nor are you providing for any future capacity. IMHO if your electrician is just swapping out a breaker panel he may be saving you a few $$$ up front and appear to be doing you a favor but he truly is not doing you a service. (no pun intended !!!)
I would like to add that in my area, once you cut the tag on the meter pan, you better have a permit to do the work. Next time the meter reader comes around and finds a cut tag, a whole lotta things start in motion. If it's determined that you did work on the service without a permit you could get fined.