We vent dryers with aluminum John, don't think you should have a problem.
Fisherman, if you have an existing B Vent chimney you can use it for your new furnace, it just has to be sized properly. If you are going with a mid and have a conventional vent water heater, likely should be a 5" chimney, if you go to a high and still have a conventional vent water heater you would need a 4" chimney. Whatever the configuration is, the contractor will put the right size aluminum liner down the existing B Vent to code.
Gerritt, good luck with the install and don't forget to send in the rebate form for the programmable stat - you will get $75 dollars back from the OPA and $15 from Union Gas - $90 for fishing stuff!!!!!! Sounds like your parents either got some added features with their furnace (2 stage heat, variable speed motor) or some contractor did very well for himself.