Russia retained more remanufacturing and repair plants plus a big chunk of the original manufacturers were also turned into repair plants, so there is likely a surplus refurbishment capacity over newbuild ones.
Yep. There are production lines dedicated entirely to repairing/refurbishing certain models of tanks in Russia. So it would be way cheaper to utilize those existing lines to improve a T-62.
In the abstract, in a vacuum, it might be better to just build new stuff. But in Russia's existing industrial setup, several refurbishment lines are available [some, if only as job creation/retention programs.] There's even more incentive to refurbish T-62 if there's abundant ammunition and spare parts for them, as well as experience from reservists. [T-62 was deployed in combat as recently at 08.08.08.]