Not too difficult:
Take bodywork and tank etc. off, remove belt covers (dunno if you need to remove frame parts for this).
Slacken belt tensioners, best is to remove them completely (2 bolts each, 1x pivot, 1x tension lock).
Remove belts (this can be a bit of a hassle, to get them over the pulleys, but no need to spare the old belts
).
Make sure timing marks are set correctly and put new belts on one by one). the driving pulley can be turned by putting the bike in gear (the higher the easier) and rotating the rear wheel by hand. Remove spark plugs for eliminating compression force.
Put tensioners back in position.
For correct belt tension: put 5 mm allen wrench between the idler roller (NOT the tensioner roller) and the outside of the belt, push firmly on the belt and tighten tensioner bolts.
Put covers and the lot back on the bike. Put all left over bolts in the tank so they can flow to their original position
.
When the belts are off, it is easy to check the valves as well, since the camshafts can be rotated freely without any force.
Good luck,
Michiel