Peter Lyons , Jan 19, 2007; 11:59 a.m.
Do whatever you like with your RAW file. Then when you're done with that, save it as a full-sized, 16bit, AdobeRGB file in psd (Photoshop) format. Do all your retouching here. (dust, any additional color correction, etc.). Save all that in the master file. Then when the client places a print order, save a new file from the master in whatever format and color space required, and resize and/or crop ONLY THAT file for printing.
As to different aspect ratios and what the client gets, all I can think of to say is that you need to explain that to them.
Not sure I've answered much of your questions, but if I've missed important parts, please clarify for me.