I don't think you can 'see' the encoding.
The problem is that different encodings use different graphical glyphs in a different way. In many cases there is no way to figure out how a particular byte (or byte sequence) should look on the screen. You should try different encodings, look at the results, and decide yourself. Of course, sometimes the guess is pretty trivial.
If the tex-file is made in a polite way, it should include a line like
in the preamble. This gives you a hint that the file uses latin-1 (=iso8859-1) encoding.
To re-encode a file -- I guess most of the modern text editors can do it. Perhaps even browsers, I haven't tried. In emacs you have to visit the file (you have to know the right encoding here) and then press <C-x enter F>. Then you are asked for a new encoding.
There are also various command-line utilities (wasn't one called 'recode'?).
Perhaps it helps,