I just finished a job that involved resizing a D300 image (same size but smaller sensor) to 24x36 inches. It was resized for printing on canvas as a soft wrap. I used BayPhoto and it turned out great. The client loved it.
A few comments. The image file is plenty big enough, but you will need to resize. Normally you should not upsize by more than 50% in a single step, so I used two steps to upsize my D300 image.
You want to minimize noise early in the workflow - and upsize early in the workflow. Many editing steps can create noise - and upsizing magnifies those artifacts. I did not apply any contrast, sharpening, or shadow recovery to the NEF file until after upsizing. That includes not applying capture sharpening and contrast at capture or import.
I had to completely re-edit my image to eliminate noise issues. Here are a few tips.
If necessary, apply light noise reduction before each iteration of upsizing. I'm talking very light noise reduction - possibly also with low opacity.
My image had some significant shadow recovery. Recovering this area before resizing created a good bit of noise when upsized. By upsizing and recovering the shadows later, there was virtually no noise.
Sharpening may be a little different. I use a High Pass step to "tighten up the image" in addition to my normal routine. Don't hesitate to apply sharpening selectively. With Unsharp Mask, you'll probably need to increase Intensity a good bit and maybe increase Radius to reflect a larger image. I also use Nik Tonal Contrast for some detail sharpening and reduced the opacity a little more than normal. The sharpenign steps are late in my typical workflow.
After upsizing to the full image size, then edit as you normally would. You are dealing with a large image file, so it will place demands on your computer processor.
I was very pleased with BayPhoto's handling of my image. Their customer service was very good.