Joyce, (Conifer, CO)
Joyce, indeed re-stringing those shades is difficult. Those that I have done in the past required holding my tongue just right as well as a minimum of three hands and a lot of time. My advice is to have the dealer perform this task and allow him to assume the liability to get it right. But this is from one with very little patience or tolerance for such things; you may opt to do it yourself if you feel so inclined.(For additional info regarding re-stringing day/night shades, see this other archived question.)
Replacing the complete assembly, however, is so much easier. Look closely at how they are hung. There will be brackets of some sort that attach the assembly inside or just above the window opening. Though attaching methods vary, rarely will the inside garnish trim need to be removed. If you’re handy with common tools, you should have no problem replacing them yourself.