Hi Darryl,
I know exactly where you're coming from I'm a noob too but maybe just a station or two further down the train line than where you're currently at. Some beginners start with using the on board self timer of their DSLRs or a remote shutter release with the aid of live view. However it seems like you want to go straight to the software side of things so I'll focus on that. My range of applications is quite small so I don't have a lot of history or experience to give any in depth comparisons but I'll do my best to help out.
Looking at what you have to work with you have the best of both worlds. Mac and PC gives you a lot of options. Like you I have both but due to the amount of software/drivers available for windows I decided to go this way (I'll probably move to Linux down the track but that's another thread
). One thing that you could do in regards to your best of both worlds scenario is to perhaps use the weaker machine (in your case the PC) to capture and then use the beefier one (Mac) to do the processing. You could then process previous night's imaging sessions whilst imaging new ones.
For capturing software as others have already mentioned your options would probably be something like DSLR Shutter (Win/Mac) BackyardNIKON (Win) and one you've already discovered Nebulosity (Win/Mac). I've never used them (I use APT which doesn't support Nikon cameras yet) but from what others say they seem to be good programs. I'm sure that someone else here can elaborate on them some more. There are others but I wouldn't really put them in the beginners category. Check the link below and scroll down to 'Image Acquisition Automation' for a list of alternatives.
http://www.astropix.com/HTML/I_ASTROP/SOFTWARE.HTM
You've also mentioned DSS which I think is a good starting stacking option for a beginner. It's what I'm using and it didn't take long to get basic results, however mastering it which I've yet to do myself will take time. In my opinion I would hold off on PixInsight just for now. I see it as the 'Gold Standard' in image processing software and believe that it may be a bit overwhelming for beginners especially if they're trying to grasp another three or four programs at once. I plan to go down this road later myself but will wait until I actually know how to take quality subs first. Processing in PixInsight looks like another universe all together.
From one noob to another good luck.