My house is about 38 yrs old and my hot water baseboard heating system was installed with iron pipes instead of copper. Im renovating part of my house and the iron pipes and fittings are expoxed because I opened the ceiling. the pipes look good with no rust. Im afraid one day they will rot. should I go through the troble of changing to copper in that area while the ceiling is open???

Normally in a heating system, the corrosion is not nearly as bad as with a water system. A heating system has very little fresh water added to it once in service, and the constant heating and cooling of the water drives most of the air from the water making the water very stable (and usually quite stinky). If this were my house, I would not change the pipes. I have done work where 50 year old heating pipes were still in great shape.