Alltel GPS with A-GPS - super fast lockon

[HeadBussa]

Hi everybody! I've just purchased a new Sprint HTC Hero with bad ESN and would like to flash it to metro pcs. I've read some threads about it but I haven't found my phone model there so that's why I decided to write here.
I called metro customer service and they said that they can flash it for $10 but I will not get internet, gps, mms or other services supported by the phone, only calls and text. So is it worth bringing them phone and let them flash it instead of doing it myself? If I let them do it then will I be able to make internet, gps and other stuff working myself? Or is it better to do everything myself? And if the last option is what you suggest I'd really appreciate if somebody give me a link for the flashing instructions.
Thanks in advance, any help is appreciated!
p.s. Is it possible to save my existing metro pcs phone number?