are you sure you need to go *that* far at all?
It could just be the rings, as silly as it sounds.
If you're feeling courageous etc take the head off and check the pistons for score marks, the pistons themselves should feel tight in the cylinders, if you can waggle them back and forth the rings are shot. If the cylinders are worn it could be the block as well, but since rings are around a tenner.. I'd start there :)