I will try to answer your questions from my own point of view.
Is it only the combined MMR that poses the risk to Autisum?
This is the one most people are worried about. However the original research that suggested a link has been extensively discredited. Many people nowadays suspect it is the combined attack on the immune system that caused problems, and not the science behind the vaccinations themselves. Others blame the chemical make-up of the vaccinations. However despite Dr Wakefield's research being discredited, when it first came out a lot of parents came forth and said they believed it because of what they had seen happen to their own children, hence why the suggestion of a link has not gone away.
and is it true that the "autisum" has always been there from the start and it just needed something to trigger it? ( i know that i may have worded that wrong and i really hope that it doesnt offend anyone it was no my intention)
Some people believe so, but the research is purely based anecdotal evidence at this time. Some people believe vaccines exacerbate autism, others (like me) believe it shocks the body into shutting down and withdrawing, but does not cause autism, just autistic tendencies (unless the child is already autistic).

also for the people that have chosen not to use the MMR do you worry about your little girls when they start to have babies? well not so much your children but your grandchildren? Is there a way around that risk?
Personally I worry very much, so much in fact that I may consider getting my daughter vaccinated with the MMR when she is a teenager, unless the single vaccines become available before then.
Do you worry about your little booys getting mumps? i think that is the one that can cause them to be come sterile? Is ther a way around that??
Again i am not trying to be mean or anything, i just really want to know
A valid question, and yes again I do worry and may give my sons the MMR as teenagers for this very reason. I believe the shock to the system will be less to a teenager than to a small baby or child.

I hope this has helped a little

T
xx