How handy with DIY are you? If you know one end of a spanner from the other then firstly (and this might seem obvious, but here goes...) read all the instructions. I know, I know, we're blokes and we hate to read instructions, but in all seriousness, the manufacturers design this stuff to be pretty much plug and play these days, so it's probably worth sitting down with a cup of tea/coffee/whisky and reading everything first just to see what's involved. Then you can figure out whether it's something you feel capable of taking on.
The HDS will be simple - I can talk you through it if you get stuck (I've done enough of them across several boats). Then you'll need to set up an NMEA2k network for your Precision 9, AC12 and NAC2 to talk to each other and your HDS9 - again, setting up an N2k network is straightforward - just a couple of power connections and that's it - everything else is literally just plugging the network leads into the backbone.
I have no experience of installing an RPU80, but again, follow the guidance in the manual/installation guide.
If you get stuck, just shout and we'll do our best to help.