I'm currently fist deep in replacing metal on one of my busses, ten panels in I think. An end is in sight though!
As far as a frame member goes though, I would only replace it with one cut from another bus. I've patched frame rails but If its as bad as you say, time to find a donor. 
Any pro body shop should be able to take care of this job for you if you have zero background in welding. 

-craig

On Jun 24, 2013, at 12:07 PM, Richard Koller <kollerr@HELIX.NIH.GOV> wrote:

> Greetings all,
> 
>                Unfortunately, I have serious " rust-out " on a front
> jacking point frame rail. The jacking point has collapsed into the rusted
> frame member. Any advice on how to handle this is needed, I have zero
> experience with welding problems like this. I'm in the DC area, so anyone
> around here who knows some welding artisans please p-mail me a name or shop,
> thanks very much.
> 
> Rick