I've used a very similar eTrex model, mounted to the cockpit, in a 1950s high-wing taildragger. Display was okay, reception was excellent - I can't imagine it being any less good in your Cessna.
If you can, mount it on the panel or yoke - handheld is a pain and will just distract from your flying task.
For flying with any non-aviation GPS, I'd recommend looking at how many waypoints are available to you, and use them for any given flight appropriately. For local flying, use the airport centre or appropriate threshold(s), and the local join/departure points. For longer trips, pre-program your route waypoints. Have these points, which are likely to have short names, marked on your chart (preferably) or kneeboard (if you can't get them on the chart).
I think on this model you have 1000 waypoints and 50 routes, so that's pretty powerful.
No idea about charts, but hopefully somebody else does.
And having done that, sell it on eBay and buy a proper basic aviation GPS for the same money. The Garmin 96 would be the obvious one in the USA, although in the UK probably an AWARE. Buy the right tool for the job and stop mucking about with walking GPSs, it's totally unnecessary.
G