Bottom line, decide on what “you” want to do with it. If you want to see it on the water and enjoy watching it sailing around the pond as it did when first manufactured then go for a full refurbishment. That would be a complete strip down, polish the metalwork, complete paint job, mechanical refurbishment and enjoy sailing it. There is a very real argument that you will have ruined its value but you will have years of enjoyment out of sailing it.
If however you want to realise the maximum value out of it then selling it as is would probably generate the best price, interfering in any way would open yourself up to criticism that it is no longer as original and give buyers the opportunity to try to push the price down.
Third option, as Ashley mentioned, a sympathetic clean up but not taking it to a seaworthy condition so you can enjoy looking at it on the shelf in its original condition.
If it was me, I fall fairly and squarely into the James May category. These things were made to enjoy operating and seen by all, not to hoard and sit on a shelf enjoyed by one. I would fully refurbish it and enjoy sailing it, happily giving up any of its value.
As an example the old Airfix P1127 Kestrel kit in the original bagging is generally regarded as being worth anywhere from £50.00 to £100.00. I bought one off eBay for around £20.00 so do I sell it to a collector and make a tidy profit? No, I ripped it out of its packaging where it has sat for around 50 years and enjoyed building it!