[Vwdiesel] engine rebuild question

[Dave]

Hi,

 I took my 82 diesel Rabbit to a local VW mechanic to adjust the injection pump timing as I just couldn't get it to run quite right. In the process of attempting to adjust the timing some how they bent one of the valves. He called and told me that it was really for the best as the engine's compression was real poor and it needed new rings. He said he would fix the head as it was his mistake and he would cut me a deal and change the rings for about $300 to $400 dollars. I called him today as it's been a couple of weeks and he told me that cylinder walls have ridges in them and that the engine had been rebuilt before and that he doubted if he changed the rings he couldn't guarantee the engine. So my question is, is he right with the ridges in the cylinder walls is that true, or is it a  thing where oversize rings, new pistons or something could work.

Thanks

Dave