your welcome.
regarding unit research:
have a look at the _ingame_ help, look up Advances.
there sometimes is a part "Military Benefits",
these are general changings for new units researched after this advance,
and sometimes also "Allows Use of",
these are special abilities you can give to new units from now on.
screenshot of "Navigation":
http://img516.imageshack.us/img516/7751/abilitiesfv2.gif
Posted 22-Mar-08 15:08 by Kaeru