How do I know if the frame is failing on my '02 Montana?

What is your question?

My driver side front door recently stopped latching correctly, and water leaked started to leak in from behind the temp/MPG readout on the ceiling. I can also hear the wind whistling outside from both the driver side front, and the passenger slider. The van has 150k miles on it, and so far has run like a charm, but in Michigan, Rust kills... is my frame starting to buckle?