Bad luck mate.
I just replaced my sight glass the other day. mine broke in my little stack.
It was pretty easy but i took my time.
I took the clutch cover off, but you could probably do it without doing so.
The sight glass is just jammed into the hole.
To take the clutch cover off.
Drain the oil
Unhook the clutch cable, It hooks into the silver hinge coming out of the clutch.
Then the silver hinge part just comes straight out. Pull it out and twist it if it wont until you get to the point where it will come out.
After that just take the screws off and pull the clutch cover off. It took a bit of force because the gasket had melded with the cover due to the heat.
Have your oil tray under the bike because a fair bit of oil comes out when you take it off.
Then just tap out the sight glass from the inside and put the new one in. Brighton kwaka recommended to use some silicon sealant when putting the new one in, apparently if you don't they can leak a bit. Just put a little bit of sealant around the outside and push it into the hole.
As i said the gasket was melded with the cover and engine, so I used a plastic scraper to get most of it off and a razor blade (again recommended by brighton) to clean up the last annoying bits.
Then new gasket on and clutch cover back on, rehook the cable and make sure it's the right tightness (the two bolts control that).
Easy.
You could do it in 30 minutes but i spent a fair bit of time on it, did it in my free time over two days (was paranoid about doing something wrong so took it easy) I put glad wrap over where the cover came off to keep anything getting into the engine.
Cost was about $16 for the sight glass and $15 for the clutch cover gasket.
Having done that I reckon you could probably just dig the broken sight glass out without taking the clutch cover off, but might be tricky. And the long way is more satisfying
