[OSM-newbies] Tunisia: converting highway=unclassified to highway=road for sketches from aerial imagery

[Joe Richards]

I have been doing some mapping from Yahoo aerial imagery in Potlatch (with tweaks in JOSM) for this area in Tunisia which appealed to me for some reason:
http://www.openstreetmap.org/?lat=36.7165&lon=10.3967&zoom=13&layers=B000FTF

I've inadvertently made many of the streets/roads highway=unclassified only to discover that this is not actually the most generic/vanilla tag, and they should be highway=road for aerial sketches.  What's the best way to convert any and all highway=unclassified ways into highway=road for that area (without affecting non-highway ways, such as forests).

Also the greenery here is basically either quite dry lawn, or kind of bushy scrub.  What sort of tags would these have?  And is surface=sand a possibility for sandy tracks, or should I stick to surface=dirt?