I have decided to buy the Finn M39 how would I go about mounting a Super Sniper 10x on it. What would I need and have to do?

also what surplus ammo is accurate in the M39?

A good bet on milsurp 7.62 x 54R is the Yugoslavian, corrosive, but good quality

Not likely you will find much encouragement for mounting a super sniper scope on a Finn Mosin Nagant, to each his own, however the Finn's are usually left alone because of their collector value in the unaltered condition,

to put a rifle scope on it youll have to probably drill/tap the receiver, your only option to leave the gun unaltered is to mount a scout/forward stlye scope on it with a no gunsmith scout mount. it will replace the rear sight assembly and you will be able to put it back to original config in about 5 minutes.

I think one of the importers used to make fake snipers out of M39's.  I got a 1-1/2 groups using the soft point Wolf Gold.  

Its not a good idea to permanently alter any Finn mosin. You would have to drill and tap the reciever, relieve the stock, and get the bolt handle turned down. They are bound to go up in value, as they have been already. As stated above, your best bet is to get the scope mount that replaces the rear sight leaf, and put a long eye relief pistol scope on it. It won't make any permanent alterations to the rifle, and can be returned to original easily.

I knew a guy who "sporterized" a Finn 91/30 with a round reciever. He had no idea it was a Finn, and a very collectible one at that. Very sad.