I have a Beseler 23 enlarger with two lens boards for Beslar 50mm and Beslar 75 mm lenses. I'm thinking about upgrading one or both to something fancy, like a Rodenstock or Schneider lens.
Can I use the same boards for the new lens(es)?
Most likely, yes.
Some lenses require different boards, because their thread sizes are different.
And some longer or shorter lenses can, for some enlargers, require cones or recessed lensboards.
But if your current lenses have 39mm threads, and you are looking to replace them with upgraded 50mm and 80mm lenses, many if not most of the better versions will use the same boards and retaining rings or threads.
You probably won't be able to find an upgraded 75mm - for some reason most of those are of the entry level variety.
You may want to consider something longer, like 90mm, if you think you may shoot 6x7. 90mm will be fine for most 6x6 or 6x4.5 negatives, especially if you have the long column version of your enlarger (longer lenses mean smaller enlargements with the same height).
By the way, there is nothing idiotic about the question - it is a good one to ask, if you don't know the answer.
One final practical point - be sure that you can actually get your current lenses off the boards they are installed on. If they have been there for a long time, they can sometimes really resist change

.
Have fun!