Hey,
Regarding your concern for conversion you may start here:
http://www.cisco.com/c/en/us/support/docs/switches/catalyst-6500-series-switches/12031-catos-ios-conversion-6500k.html
Moreover you may use the configuration conversion tool but i am not sure if it will convert all the commands, you may have to check the configuration guide for rest of the commands:
http://www.cisco.com/c/en/us/support/docs/switches/catalyst-6500-series-switches/70273-70273.html
HTH.
Regards,
RS.