Firstly, dust does not hurt electronics unless enough is accumulated on electronic components to act as a thermal insulation, and that is not going to be a problem with the PDA. Any electronic device in your home that has ventillation (radio, TV computer, etc.) is likely to have a healthy accumulation of dust inside it.
Second, the headphone jacks that they put in the Palm PDAs are very tiny and not of very high quality. They are a rather frail mechanical device.
The average PDA user is not going to be able to "fix the problem" by replacing the headphone jack if that is the problem. If you have ever had a Palm PDA apart you will know why the average guy is not going to replace that jack. For one thing, finding a replacement part is not going to be easy and maybe impossible. Performing any kind of surgical procedure on that jack is virtually out of the question.
The method I suggested of "wicking" a small drop of WD-40 into the jack will not put enough lubricant in the PDA to get onto anything but the jack. I know this to be true because I have had the back off my TX while wicking a small drop of WD-40 into and I could very easily see where it went, and where it did not go.
If the jack is the problem, and if WD-40 will NOT fix it, THEN you will have to find another way to fix it.
Go for the simple, non-destructive solution first. Then, if that fails, go for the more complex and expensive solution.