Jim,
I've just bought 2 X Spirits for me & the wife and fitted the autocom speakers to them. Its actually really easy.
Just pull away the internal cheeck & head padding carefully. This should be attached to the main structure with little poppers. It is designed to be removed for cleaning so you will not damage the helmet at all.
Arrange the speakers in the ear recesses and feed the wiring behind the padding. You can then route the connection cable out of the helmet at the most convenient location.
Use insulation or duck tape to keep the wires in place and then re attach the padding.
You will then need to try the helmet on and adjust the position of the speakers to suit your ears. This is trail and error at first but if you play around with them you will eventually get the positions just right so they are comfortable.
When the speakers are fitted, the helmet feels a bit tight when putting it on but if you locate the speakers correctly, you will not feel them or any of the wiring once the helmet is on.
Easy - peasy and should only take about ten minutes - no cutting or anything involved.
hope this helps
Chris