:type: well, first thing, fire is not a model but an "effect".
I dont know if u 'll be able to get a little torch, but fire is easy avaiable:
- go to the BASE and create a new folder, call it 'effects'.Then open 'therest' w/WinZip or Winrar and select all .efx files: extract em to the new folder just created (be carefull: Pk3 must keeep inalterated). [In Winzip select/or keep selected the 'use folders' options for a correct distribution of .efx files into their own folders inside the new effects folder just created in base].
- open ur map in Radiant; rigth mouse click > fx > fx_play_effect:
a little red box 'll appear. Taking it selected open the Entities window by pressing N. Then add the key pars required by the effect u r looking for, that is, key: effect - value <wryte the path here> . Example:
fire/col2_fire.efx. Press ENTER and compile.
Maybe u 'll spend a lot of time searching all over the effects folder the fire u need for ur torch (there r big and little fire effects etc. ect.). Maybe no one of that effects is suitable 4 the work u have in mind. In this case u can work whit parameters traying to modify the effect. The last solution is to edit a new effect. Good look

.
Second question: dont need decompile maps to work w/ others mappers textures and materials.

Just read 'using custom textures' threads in this forum. i.e.
http://www.gamingforums.com/showthread.php?t=106706
(Also check this big source of textures and texturing tools:
http://www.texturemaker.com/
Finally, if u wanna look deep inside maps to learn how experienced mappers works, then get the .map sources files and explore em in Radiant:
http://www.sof2files.com/file.info?ID=8950
Hope this help