do restored stocks on a gun hurt the value of the gun ?
Well, that's a loaded question...usually a gun that needs grip restoration is not in very good shape as well. You do not find mint stocks on an 85% gun unless they were taken off and replaced with another pair of stocks.
If you restore a pair of 1978 K Magna grips, you'll never get you're money back. You are putting more into them than they are worth. A restored pair of Cokes just brought $568 on eBay. So, a restoration of Paul's quality is warranted and justified. Only some stocks are worth saving.