I haven't had a chance yet to put my hands on a Garmin Colorado
but I'd be very surprised if you cannot easily download your recorded trails from the device to your computer and upload trails you may get from wikiloc back to the Colorado.
To do that you need some software, if you didn't get Garmin Mapsource with the receiver, you still have pretty good options (free) like G7ToWin and GPSBabel: you may find some help here:http://www.wikiloc.com/wikiloc/help_g7towin_en.html
Regarding buying topo maps, I'd say that at www.compegps.com
you'll find highly detailed maps of Spain.
It'd be great to know your advances on this subject on this thread since your device is pretty cutting edge and probably others will face the same issue from now on.