I'm right there with you Bob, not being up to speed with Linux, that's one thing I really enjoyed about this project, pushing myself outside my comfort zone...
I also needed lots of light and a magnifying glass to make sure the solder work was all done well. I've mentioned this before, I really don't care for the purple color of the board, it looks nice and all but once you solder up the board the color is too dark (as opposed to say the standard green boards) and it is very hard to see the solder joints clearly with the naked eye. So it may be partially that we are getting older, but the HM board is hard to see and does have some solder joints that are very close together. That and the fact that there are traces on both sides of the board (and solder doesn't seem to like to flow between them) makes the HM board not the easiest thing in the world to solder up.... and I've done LOTS of soldering...
On the network issue, I see no reason from a hardware standpoint that both network adapters can't be used, though I admit I am less than a novice as far as Linux and the HeaterMeter code goes. I've done lots of networking with Window's and there is no problem assigning static IP's to multiple devices (or multiple IP's to a single device for that matter), so I did not approach the WiFi/LAN setup on the rPi with any caution or expectation of difficulty when set them both up.
For me it went very smoothly, I first set my pc to have the IP 192.168.200.XX, then connected it to the rPi with a Cat5 cable. I then used the HM interface to setup its connection to my WiFi network, then set the static IP for the WiFi that I wanted (192.168.1.99). I unplugged the Cat5 Cable and tested the Wifi connection (good). Finally I went back and set a static IP for the wired LAN that I wanted (192.168.1.98). I tested connection to the HM web page over both IP's and it connected fine with both, I had no problems at all. I've booted the rPi with just the LAN cable connected (no WiFi), with just the WiFi connected (no LAN cable), and with both WiFi and LAN cables connected, in every scenario it seemed to work perfectly. I've also connected to the rPi via PuTTY from a PC that is wired to the WiFi router and it connected fine on both the LAN and the WiFi IP's. So I've yet to see any problem....
Bryan did take the time to explain to me why it shouldn't work, and though what he said seemed to make sense, I've not had a problem using a static IP from the same block on both my WiFi and wired LAN on my rPi....
PS Speaking of outside the comfort zone. I am pretty close to pulling the trigger on a 3D printer, I know Bryan has just made the move himself as well. Now THAT is gonna be well outside the comfort zone! LOL