That is very sound advice. Make sure to also check the inside of an old used bayan.
You may find all sorts of problems inside. Buying a used Russian bayan is really stepping into a minefield.
Here are just a few examples:
Reed plates that should be easily removable (with hooks or screws) were glued so they could not be removed. Also, piccolo reeds that should be upside down (for better response and the possibility to do tuning inside) were not upside down.
Excessive scratching and use of dremel caused significant rust on the reeds.
Poor thin foam gasket under the reed block instead of a proper leather gasket.