the classic doom 3 team built their maps from scratch, they are not the same exact maps from the shareware or registered versions of DooM
while there is a tool that can port DooM 1 and 2 format maps they look exactly the same after being ported, these guys used no such tool
and for the sprites, for the limitations of the original and id updated 95.exe engines the sprites are pretty good, i said nothing bad about the sprites at all originally...
*sigh* i have the feeling what im saying is getting lost in translation...
im not flaming you, im offering to help you convert your project in such a way that you should not have to worry about any form of legal issues
edit
use your resources and modify this and you should have no issues at all
http://freedoom.sourceforge.net/download/