What maps are we talking about here??
All open maps are free and have no restrictions.
If you are trying to use a Official Garmin maps then you will have a problem.
From what I understand some of the new Garmin Units at this time can not be patched.

If I were you and you really need an official Garmin Map other that what comes with the Garim 785 then pay for it.
This unit comes with all of Europe and most have life time map updates.

Or just use free TOPO maps of the area you need.