If you are used to electronics and have a few hours it's relatively easy to open up the pot and clean the carbon wipers. The short term fix tends to stop working after a while. I guess you could sell it while it works but there's a chance the new owner would receive it not fully working.
I always find that tough to recommend because there are so many technical details to take into account depending on the electronic and physical design of the amp. Ultimately though it's probably best practice.
If you are used to electronics and have a few hours it's relatively easy to open up the pot and clean the carbon wipers. The short term fix tends to stop working after a while. I guess you could sell it while it works but there's a chance the new owner would receive it not fully working.