Tell your mate to consider the following:
1. Norlins are going up in price steadily.
2. LP Deluxes wth goof rings are more scarce than other LP Deluxes, simply because there were not that many fitted with them, ergo, their value, I believe, will be proportionally greater.
3. If it's all-original, don't modify it at all. It's a great instrument, as is.
One thing that may need to be looked at: has the bridge been turned around in order to accommodate accurate intonation? If so, it may need a tech to set it up properly (i.e. correct truss rod adjustment), so that the bridge sits correctly once more.
Hope this helps.