10.6.3 DVDs can be bought and you have to call Apple to get 10.6.x on the phone which people still need to do in order to upgrade to Lion or Mountain Lion (10.7 and 10.8)
And no you do not need to take it in!
You have to have a 2008 3,1 model Mac Pro to install ML.
As for secuirty and taking it in, if you were to, just remove all the hard drives etc and slap a new empty hard drive in there.
But Apple Store customer relations support must have Russian customer support.
They have 10.6 DVDs on hand but were removed from Apple Store web site (and now seem to be searchable or back)
Snow Leopard came out in August 2009, Lion in July 2011. And now the download almost only method (be sure to save to disk and flash drive before using).
I've seen SL DVDs online like Amazon sell for US$200 as a result.
In the US, there is a central Apple Online Store that will accept credit cards from US buyers and ship to US addresses.
In Russia, there does not appear to be such a central store, so you would have to contact the sellers on this page: