New to Snowmobiles Question on Shocks

I just picked up a 1994 AC EXT 580 EFI for cheap.... $100.... runs great first pull start.... Im looking to replace both rear shocks. I assume both are stock one is a 0604-311 and other is 0604-755. Its a sled for my 10 year old to have some fun with. I cant in good consience spend 3-400 on shocks on a $100 machine so its a 2 fold question. Are these shocks rebuildable? How can i tell? Also if i dump <$100 on 2 kimpex or SPI shocks how upset will i be

New to Snowmobiles Question on Shocks