Meridian 508,20 upgrade result in new laser?

Hello I am thinking of buying a Meridian 508.24
that was upgraded 2 years ago, and was wondering
what exactly is done to the player. I would especially
like to know if the laser assembly is changed.
Probably not(unless something was wrong with it). The electronics are the main update from 20 bit to 24 bit. Everything else stays.
thanks Bidtee