Is my vehicle at risk of CO poisoning?!

I have a 2002 Ford F150. The exhaust sounds terrible and I've been told that the right manifold needs fixing. Is my vehicle at risk of CO building up in it if I have all the windows up? This concerns me a bit as we are entering winter and obviously I can't have the windows down. It's an old truck with lots of rust so I'm concerned that exhaust could leak into the vehicle. Any thoughts would be helpful. Thanks.
Added (1). @Keith, how is it that CO can build up in a vehicle and kill someone. I mean, aside from the obvious stupidity of hooking a hose to the tailpipe. I'm talking about unknowingly. I've read some news articles about this happening to people and I just want to make sure my vehicle isn't at risk of this.

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