i'm impressed that your clutch lasted this long.
it's very easy to replace the disks/plates. i'd recommend looking at a barnett stack as a less expensive and very good alternative to OEM. check out motowheels.com or ca-cycleworks.com for vendor options aside from your local dealer.
if you only need to change the clutch stack (as opposed to the basket and/or drum in addition), it should run you about $150 for the clutch pack which is very easy to install yourself. unbolt the clutch cover from the right side of the motor, unscrew the 6 bolts that retain the clutch springs, slip the clutch pressure plate off, slip out all the disks/plates from the drum, and install the new pack. note the document included with the stack for proper stacking order. reinstall the parts you removed and away you go.
while not complete, here's some pics on dissassembling the clutch. note this page is for a full clutch kit removal which isn't the extent you have to go to for this:
http://www.ducatipipemod.com/s4/mods/clutch/