Can't help you with the normal map conversion part, but if you want to convert the high poly mesh for the normal map to a low poly version, try this free tool:
http://www.paralelo.com.br/en/solucoes/tecnologia/progmesh/index.php
There's another poly reducer program available at:
http://www.thegamecreators.com/?s=0&f=action3d
These are useful for doing quick and dirty reduction, but manual reduction is probably the best way to go for serious modelling.
http://www.paralelo.com.br/en/solucoes/tecnologia/progmesh/index.php
There's another poly reducer program available at:
http://www.thegamecreators.com/?s=0&f=action3d
These are useful for doing quick and dirty reduction, but manual reduction is probably the best way to go for serious modelling.