Maintaining DPI for hi-res printing.

OK Photo-Paint users,

I thought of a question that has been bugging me for a while. Perhaps you could shed some light on this for me.

I am confused about checking and maintaining the dpi of a hi-res image.

Here is my usual situation:

I take a high-res image using a Canon 20D which shoots 8.2 mega-pixels.

A typical image size is 3504x2336 and it's between 3 to 5 MB depending on the image of course. The camera saves them as .jpg

I open it in PPX3 and do a few things to it and now I want to save it at the same hi-res it was in the first place.

Is it best to just do a Save-As and maybe choose the TIFF format, or choose .jpg with no added compression and a 4:4:4 sub-format?

How do I check what the dpi was in the original photo?

Should I be using Image / ReSample to save it?

Resample always defaults to 72dpi for web images. If I bump up the dpi setting to 300, does that have a bad effect on the image?

Anyway, what's the best way to maintain the highest resolution for printing large images?

Thanks in advance!