MOBILE NETWORK shuts itself off while I'm using it as modem

Ok so I accept the the Aria isn't built to act as a modem and accept calls at the same time 
Now....when I'm using it as a modem, I'll be in the middle of doing something online and for no apparent reason my connection is lost!  When I check the phone, the MOBILE NETWORK has disconnected itself. Sometimes I have to re-check the box and sometimes it will come back without me checking it manually. So far, using the Aria as a phone, great! But as an internet connection, not so much. Any clues?

PS my friend has and iPhone that she tethers to her laptop while she is here and she never loses her mobile connection. Rethinking my purchase...

I don't know what Gingerbread is, other than an upgrade. I have froyo 2.2 and connection using it as a modem sucks. I see that Gingerbread may fix connectivity issues. I am not very computer literate. One YR ago a friend taught me to use a mouse, keyboard and CPU. And Facebook  and email. I've progressed I believe considering my complete lack of computer or internet knowledge.

So...can someone please give me simple, step-by-step instructions for how to find, Dow OAS and install Gingerbread??

I will be immensely grateful!
Thx