I ignored a dripping noise in my utility room that has, of course, gotten worse. A few days ago, after several days of heavy afternoon showers, I was vacuuming the carpet in our finished basement and noticed that it was wet against the wall to the utility room. There was a pretty big puddle of water around and under our gas furnace, with no water visibly dripping from any of the various pipes (or the hot water heater or anything else). However, I did see water dripping from the gas vent (also shared by the hot water heater) onto the furnace, down into the furnace itself, and condensation on the outside of the main duct exiting the furnace for the vents. I checked the attic, where that gas vent pipe goes out through the roof, and sure enough, I could see daylight and the insulation around the pipe was damp. I've call a roofer to come check the seal around the vent pipe and to make sure the vent pipe has a cap on it. So my question...

This may be obvious, but should I have an HVAC tech out to inspect the furnace/AC? Any guesses on what kind of damage there might be? I didn't see any obvious signs of rust when I took the top front cover off it and the blower still functions when the AC kicks on. I know we need to replace carpet, baseboard, drywall & possibly the 2x4 support system for the wall because water has been wicked up it and mold is forming (shudder) - I dread having to possibly replace the furnace as well. And while I'm talking about replacing things, should the entire stretch of the gas vent from the furnace through the roof be replaced? There's no way for us to visually inspect the pipe from the basement ceiling through the 2 main floors to where it comes out the attic floor - would the HVAC tech be able to inspect/test the integrity of the vent or even need to do that?

Any help/advice is much appreciated, as this is my first new house and this is our first major problem in 5 years.

It is probably OK,, as the water probably ran down the outside of the vent, and not the inside where it could maybe do some onseen damage,, just keep an eye on it and if the roofer did his job, all will be well

HVAC tech is here as I write this (roofer has not showed). Drain line from AC unit, which sits on top of furnace, was clogged, which lead to overflow. Called them today because HVAC system fan/blower would not turn off. Furnace circuit board is fried from water damage. He's cleaned out the drain line and is installing a water detection shutoff thingie, which will turn the AC off if water ever overflows again. This thing is now also part of code in my area (N. VA). Because I have 2 zone heating/cooling, I'm having him clean the drain for the upstairs system & installing the shutoff thing up there too. And he's doing the annual maintenance, which we've never done, on both AC units. So for the HVAC system alone (not including drywall/carpet/whatever repair from water damage), we're looking at $1500. It pays in the long run to do annual maintenance - now if I can just convince my SO of this...