LA 140 PTO Repair

I have a JD LA 140. Recently my PTO clutch will not dis-engage.. I'm not sure if the pto switch has just gone bad or the clutch itself.
I have a couple of questions listed below.:

1)How can I confirm where my problem is. (Switch or clutch)
2)If the clutch is bad how hard is it to replace. Can I do this job by myself?

Any help would be appreciated...

Thanks