Speaking from personal experience, bird cage repair is not all that hard, it just requires taking most of the car apart, which sux.
You would not have been able to do it only with the dash out, but it does have to come out, as does the windshield. You could get lucky (not likely) and be able to get to the lower corners with the front clip in place. I'll post my pics of all this tonight. If you don't go ahead and do this repair, your going to get more dammage. Ruse being a chemical process does not stop on its own, it will only stop when neutralized and chemically stopped. It will continue to leak and you will get rusted floor pans, rotted carpet etc.
What it entails is removing the windshield, remove the dash, remove the front clip. This will expose all the top of the firewall, lower windshield frame, corners etc. Clean the whole thing REAL well with a brushwheel and see what you got at that point. I ended up fabbing a new drivers side WS frame corner, 2 patched along the top WS frame. It takes a bit of cutting, heating, pounding and welding, but it all went together. Primer and paint and put it all back together.