It ain't hard, there are vids on youtube to show you how to do it. Hardest bit is getting the covers off... Worth noting the belts are fairly unique and there are no bargains to be had at all, you're looking £110 for the belts, wherever you look.
Had mine done at 2200 miles in 2007 at JHP just after I bought my 900ssie as it had only had its first service, the bikes now done just under 10k and they are still on so only 4 yrs overdue. Hardly had chance to use the bike due to two redundancies but for peace of mind they are getting done next month.
paul if you have doubts about your own skills re belts then strip the bike inc bodywork and belt covers and have garage replace belts and do everything else yourself.