It's really not that hard using Topo 10. I'll assume you've managed to unzip the
.gpx files out of the compressed directory on the AC site.
Open Topo and select a new project. Click on Route, then use File -> Import, and navigate to the right folder, then open the right .gpx file. Save it as a file using the New/Edit button on the far left.
Plug in the GPS and turn it on, then click on Handheld Export. Export the route and store it on the memory card.
I've got the older version, so I'm not sure what the capacity of the PN-60 is. Mine only takes cards up to 2 Gb, and the full route, with the appropriate state maps, takes almost 6 Gb. If your unit can't take an 8 Gb card, you'll need 2 x 4 Gb or 3 x 2 Gb to carry the entire route.
FWIW, pfaffing with batteries and routes was more trouble than it was worth for me. I can only remember 3 places where -- if I had had the GPS on and turned to the right location and track -- it would have kept me from missing or worrying about the right turn. The AC maps really are that good.