Depends on the extent of the damage. nemo is right, as long as you are not going to have to scrap the block you can have it bore or just honed for dirt cheap. If you can take the engine down to bare block on your own, and can use your old pistons - I would say a rebuild could cost you around $600. That's for bare minimum, though....block hone and passages cleaned, new rings and bearings, gaskets. I would call a local shop and ask them the cost to hone a 6 cylinder engine, then gather a parts list and look up cost with one of the site sponsors.