I've printed a number of 20x30's. The images from my 6.1MP Fuji S1 were OK. If you have Genuine Fractals and can upres -- do it. You have a 3000 x 2000 capture -- which when stretched over 30x20 inches gives you 100 ppi. You should double that for an effective print.
As far as profiles and such -- depending on the lab they can provide test files with matching prints or a profile for their lab process. However, here's a way to test the complete process cheaply. Figure out what a 5x7 section of the image would be. Pick an area that has detail, light, whatever's really important in the image. Crop it, size it it 5x7, and have them print it. Costs a buck and you get to see the exact product you'd have at 20x30. You can take a magnifying glass or a loupe and look real hard at the detail and see if you like what you see.
Best of luck
This is hanging on my studio wall in 20x30. Captured with a Fuji S2.