By Doug Mielke -
Have a look at Bomgar.
bomgar . com
Self contained, no 3rd party server so very secure.
Access from simple desktop view > full system access > remote, unsupervised
Folks at the other end can manage the degree of access you have.
In temporary instances, it self-uninstalls at the end of a session.
Nothing left over.
I have used in the past and is very solid / flexible.
cheers
Doug