My experience over the years with BarsLeaks has actually been pretty good.
I don't know anyway to neutralize it, but since you're replacing the radiator anyway, I don't think I'd worry about it too much.
BarsLeaks only seems to cause problems where there are small passages such as radiator tubes, and even then I've never seen noticable problems with it. The heater core may have had a little of this, but I doubt that it'll be a problem.
I believe I'd get it in the driveway and flush as much fresh water through the system as possible before changing the radiator.
If you really want to get serious, there are many radiator flush products your could use. Again, if you do that, run lots of water through before changing the radiator, to flush the flush out.
'84 Euro 240D, 523K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in