The D800 or D800E are up to the task.
I assume you know about having even , no glare lighting, and about shootign raw files (NEF) oinstead of JPEGs.
As for input I would look at two toolsets: The Xrite ColorChecker Passport system (target + software) or Datacolor's SpyderCHECKR target and software. I use both but these days have been using the Datacolor SpyderCHECKR more often. All cameras have a color bias and the goal of both of both products is to neutralize those color capture characteristics of your cameras.
The Xrite ColorChecker Passport system creates a custom Color Calibration program which works in Adobe Photoshop Lightroom and Adobe Camera Raw. You shoot an Xrite 24 patch ColorChecker target and the software builds a DNG calibration for your camera based and you choose that "profile" ( it is not an ICC profile) in the Camera Calibration tab in LR or ACR. it works well in my my experience but I've read some complaints that the profile created was too contrasty. Without knowing how they shot or lit the target I note but reserve judgement on that criticism.
The SpyderCHECKR works differently. You photograph the target and after making any necessary exposure adjustments in Lr/ACR you export a processed version of the file and open in it the Datacolor software and it creates a preset of H/S/L (hue/saturation/lightness) values which you can apply during either importing or when processing images shot previously with the same camera.
Both the Xrite and Datacolor products are user friendly to implement and produce excellent results., . The end result differences are like the differences between two vanilla ice creams - which flavor of neutral color rendering do you prefer.
For output I would be looking at an Xrite i1 Pro 2 solution. I haven't been happy with the results from other products and I am pretty picky.
Regarding the need for stitching: you might need to or you might not, it depends on what surface you are printing on. Canvas, textured and matte papers have a far lower resolution than gloss or semi-gloss media so a single D800e frame might be absolutely fine with no interpolation at up to 40 inches and possibly more. It also depends on the
printer you are using. The native resolution for the first rate Canon iPF and HP DesignJet series is 300/600dpi while Epsons have a native resolution of 360dpi.
If you do need to stitch for this kind of work you'll be best served by a lens that allows you to keep the lens stationary but shift the camera body laterally and vertically.
As to lights: As I said before you want very even lighting from corner to corner to center. By very even I mean within 1/10th of a stop. You also want the lighting to be consistent from frame to frame and from power settign to power setting. I like the Broncolor pack and head systems and the Paul C. Buff Einstein 640 monolights for this. When photographing painting I prefer to use polarizing gels on the lights and a polarizing filter on the camera. This called cross polarization as the polarization axes are at a right angle (90 degrees) to the orientation of the filter on the camera,. Some people believe this is unnecessary however.