are there any tools that let me rip 3d models from psx game? also are there any modles that let me replace on model with another?

Many companies used TMD for the model format.  However model ripping is not easy. Not because the model information itself is not accessable but often the animation format is a pain.  I still have nightmares of FF7's crazy format for the animations.

I know all you want to do is RIP stuff but there aren't many ways to do this with PS1 games.  PS2 games are more prominent in having models ripped from them because more people are interested in those. 

Cyb

for ps1, http://mirex.mypage.sk/index.php?selected=1

That program will do everything you want. It's a ff7 dude editor. It works on a bunch of other ps1 games too.

I don't know try it out.