Is this a 700 twin (Polaris) engine? If so, it will take you less than an hour to have the engine on the bench...(personal best on my old 700 RMK was 42 minutes from rolling it in the shop to engine on the bench, but I had WAY TOO MUCH practice pulling that dang thing out).
Like SEG said, you may be able to assess the damage by removing the head and cylinder. Replacing bearings on the crank (especially inside bearings) is best left to the pros, it takes some pretty specialized tools to pull the crank apart and then get the bearing and crank back together again in phase. If the crank is damaged, you may also need case work. It's pretty easy to put more money into an engine than a sled is worth.. (new OEM crank is about 950, case is about 550, seals and gaskets, another 150 or so, cylinders, 400 ea, pistons, 150 ea)
If it has small metal chunks on the piston, probably one of the bearing cages let go or the connecting rod bearing let go. If it's the top rod bearing, that can be replaced without removing the engine, but if it's the lower, you will want to take things apart to assess all the damage. You may want to split the case regardless to make SURE there are no small pieces lurking about the bottom end, waiting to destroy your crank.
About the only specialized tools you will need is a flywheel puller and a good torque wrench If you do the work, get a manual. It's the best money you can spend. If you buy a flywheel puller, get a stout one, Polaris flywheels are notorious for being stubborn to take off. A cheap one will break and can damage the stator under the flywheel. A special wrench to torque the cylinder base nuts is nice, it's impossible to get a socket with a torque wrench on all 8 of those. A crows foot wrench will work in a pinch.
You may also find a manual online, there are several posted in the stickys in the engine/drivetrain section of the forum.