Easiest thing to do would be to spray some silicone on the weatherstripping; it dries out over time and silicone keeps it supple and effective. Next, you could take off the door panel and check the moisture barrier for any holes or improper seals.
On radar detectors, I think a cheap radar detector is more dangerous than none at all because you are lulled into a false sense of security. Having tried several other detectors, I'd settle for nothing less than my V1. This has been discussed ad infinitum on this site before...
