AM JUST ASKING!!!!

I own the Lg Rumor Touch on Virgin Mobile, it is a pretty fair phone if you just want to txt your friends, call people and surf the web, this is a phone that has plenty of power to do that. but if you want to really interact with your phone you might want an android or an iphone, i got no job so i cant afford a 2 year contract paying 60 to 80 buck each month, so i will want my $25 plan on one of those nice phones.

am getting an htc hero for free (sprint) i would like to know if it is possible to activate it on the the Virgin Mobile

I saw some where that it was possible to clone the ESN and write it on the phone i want to activate, it is illegal but is it legal if i own both phones, am willing to to throw my rumor in to my drawer and never use it again.

if it is possible plz let me know if its legal and how can it be done!!!
thanks before hand!!