Get your contacts into gmail contacts (into specific group, you may create group "phone"), and read this:
http://androidforums.com/sprint-htc-hero/15382-if-i-create-another-gmail-acct.html#post139948

It works perfectly

 

oh, and when you add new contact on your phone, select "Google" in contact type. This will keep it in sync

 

Just google for something like "Convert IPD to csv", i'm sure you'll find something.
Then import csv file into gmail contacts (it has it option)

 

IF YOU have outlook on your PC you can import the contacts file. then export to your google account. Then sync the Hero with your google acct. under settings, data synchronization... google.