Need Some Art Prints Made!

One of paintings that recently sold on etsy.com, the painting that was featured in a newsletter, keeps getting marked as a favorite and placed in treasury lists. It was a one of a kind item, an original painting. I did however make a high resolution digital file of the painting with the thought of making an art print later. I have been researching and trying to discover the best place to have some art prints made. I also want to consider greeting cards of the painting. But, first I will concentrate on having some prints made. I am finding out rather quickly that there are a lot of options out there. There are different requirements for different companies. Some printers request CMYK and 300 dpi, which was the standard when I was working in the printing industry many years ago. Some printers that do digital printing request that the file remain in RGB color mode and a JPEG file. It's all interesting. I may go with the easiest thing to start with, which is to keep in RGB and a JPEG and see how that goes. I will tackle the greeting cards and all those options later.