For the flame sabers just look for them at JK2Files, there's like 5. I mixed a few up for my own mod.
For the fire-instead-of-lighting effect it wouldn't be THAT hard, just a lot of work. For Blade I hunted down almost every shader that had lighting and replaced it with fire effects. This was for Reapers force-flame and my GEP-into-Flamthrower effect so you wouldn't see that dumb lightiing.
As for hitting a guy and seeing flame there are several different ways you can do that, by changing the fleash-impact.efx file:
1- Replace the fleash-impact effect with fire instead of sparks. Easiest way.
2 - Chage the shock effect into a fire effect, and add an effect like that of the tazer or force lighting. This takes alot of work to hunt down the shader.
3 - Add an effect that actually shoots out flame. Master Cheif had a small mod like that.
Note that this will NOT give you more or less damage, it'l just look different. Aslo add in a smoke effect after the flame, it looks cool.