i wouldn't wast my time replacing anything.
just cut out the inner brace like i described earlier. get some wood and a BFH. pound out most of the dent,straighten the inner brace on on something flat, pop rivet it back in like i described, them re install the window. probably take you less than a day from start to finish.

as a experienced body man i could do the job in about 2 or 3 hours.

perception is 90% of reality