[Skarsaune]

If preserving the value is a concern, leave it alone.

Personalizing/customizing instruments is rarely a value-add when it comes to resale. The next owner may not view your upgrade as an upgrade.

Kind of like tattoos, in a way. ��

But if you want to, by all means, have at it. There are some absolute wizards when it comes to inlay work.

Edit - on further thought, and looking at the Nichols inlay site, get an inlayed truss rod cover. You can personalize your instrument but go back to the original if you ever do sell it.
The J-15 I bought came with an inlayed truss rod cover. It not suiting my vision for that guitar, the original promptly went back on.