Most printers will prefer images using the Adobe sRBG colour profile, but that can vary from printer to printer, so it is best to check with them.
Resolution matters more on how an image is going to be viewed, and I wouldn't list that as a primary concern when getting something printed up. I've been happy with results from resolutions below 100dpi, which works well enough for a wall hung sunset, although I'd go higher for portraiture.
There are other things that you should consider when selecting a printer; such as whether they laminate the prints or whether the frame allows for adjustment as the canvas stretches over time. Some printers only use polyester canvases, which some believe doesn't give as good a finish as cotton.