texify (or pdftexify) is merely a program that will run (pdf)latex (and, if necessary, bibtex, makeindex, and what not) for however many times it takes to get all cross-references, citations, index commands, etc sorted out and resolved properly. Hence, as long as you've set your pdflatex program to run properly with pstricks, e.g., by specifying pdflatex -shell-escape, you shouldn't encounter any problems with pdftexify.
You can't get TeX to find text in a png the way it does for psfrag as essentially the information just isn't there (even if TeX could read the binary file). However if the png image has no text at all you can overlay latex text over it. there are packages to help that but you don't really need a package.