If you're going to do this yourself, get a 4" grinder. Get a wire wheel to fit and a few cutting wheels.
Use the wire wheel to find the factory spot welds. you have to drill them out. Go to the aformentioned site and look it up.
Use the cutting blades to cut off the bad metal.
I also have a Dremel to make small cuts.
It takes alot of fitting to get it right, but it's not something you do more than once if done right.
I have a thread on
www.vwrides.com in the bus forum under "74 Westy" . It might help.
If not, check out the other threads- PPP on there is a metal wizard.
Don't be afraid to go for it. I built my '58 bug without ever having welded before and I literally replaced the bottom 6" of the whole car.
It's also on there under " Saved 1- not for purists" in the Beetle forum.
Here's a quick synopsis