Nadine,
Lots of questions!! I wrote a blog post about giclee printing that I think would be helpful for some of your questions.
http://madebykimhoffman.blogspot.com/2011/03/giclee-prints-part-2-paper-and-ink.htmlThere are many great books on giclee printing and digital imaging that will take you step by step through most of the questions you asked.
Making a giclee print is NOT a matter of just having the right equipment and archival paper, it is also having years of experience in digital imaging, color correction and printer mechanics.
I realize that professional photography and giclee services can seem expensive but be careful when you invest in a printer because you can easily spend much more.
If you find the right professional giclee service, you will be in control of your end product. I've worked with hundreds of artists and gone through tons of proofs. You just need to be absolutely clear about what you want and ideally you need to work face to face with someone. Talk about your artwork with the service provider; explain what colors, textures, shapes, etc are important to you. Talk about the size(s) you intend to print before the scan is made. And always make sure you get your print file and the highest resolution image that was scanned on disk.