I have an old house, approx 100 yrs old- the living room and dining room are paneled, I'm assuming over old plaster. My guess is that the plaster behind the paneling is in bad condition, and that's why it was covered. I want to just have drywall hung in both rooms, but want to know if I should have it hung over the paneling, or have the paneling removed to see what is behind it and then hang it over either the plaster or beams, whatever is there. I am curious to know what is behind the paneling, and also would like the opportunity to add insulation if possible- but I also don't want to open up a whole can of worms by removing the paneling and finding a disaster behind it.
I plan on hiring someone to hang it- if they remove the paneling and find that the plaster behind it is a mess, will they need to rip it all out? Or can they just hang the drywall over it? I'm also trying to keep my expense to a minimum, and don't want to find out that anything else needs to be done.
Please let me know what you think.
Thanks.

If you want to add insulation then you really need to remove the paneling. Maybe start with one of the smaller walls and see how it goes trying it that way.

If the plaster is in bad shape, though, will they be able to put up drywall over that? Or will they then need to tear out the plaster?

I have put paneling and dry wall over plaster with no problem. It isn't hard to take the plaster down but it does make a dusty mess.

The other variable is how long are you going to be there? If you are in it for the long haul, personally I would tear down the paneling and start there with fresh drywall AND maybe repair what was being hidden?