It only took a couple of hours to install the SPX-5R. It really is pretty simple. Hardest part for me was finding some room to mount the course computer. I wound up buying a Navpod to mount the P70R control head because I had no dashboard space to install it. That took another couple hours to cut out and drill all the holes. To connect the HDS7 to the SPX-5R you just connect the 4 wires labeled RS-232 (in the same blue plug as the power) to the NMEA 0183 terminals on the course computer.
One other thing I learned that wasn't quite clear in the instructions is that you cant wire the P70R directly to the course computer. You have to hook up both the course computer and the P70R to the SeaTalk 5 connecter block, and then plug in the blue plugs to any unused terminals on the 5 connector block. Also the course computer does not supply 12VDC power out on the SeaTalk cable, so you have to use the SeaTalk power cable and plug that into one of the terminals on the 5 connector block.
I dont know if this all makes sense or not, feel free to contact me if you need any info.