imann, i dont remember the prices, but i do recall seeing a scanner on the HP site which could handle 42 inches. if you're planning on doing large format scanning on a regular basis it might be worth looking into. if not, i'd try to find someone local who could handle those sizes and have them do it.
the biggest problem with oversized scans is, shadows and a loss of texture. as you bend the material in the scanner, the outside edges arent going to show up right because they are partially lifted off the scanner plate. thus, you often need to overlap your scanned area and then do some fancy cropping and joining.
orientation is ususally fairly easy to handle due to nice straight edges on the scanner surround. you simply keep your material flush against that edge, or, if your scanner has a 'buffer' zone on the plate that doesnt scan, cut yourself a strip of something firm to use as a guide for your material. put this on the plate over the buffer zone and use the edge of your cut piece as your guide. i had one scanner that had about a 1/4 inch buffer zone along at least one edge. i got used to putting my material along a different edge
craig