Replacing rocket launcher worldmesh with one from LWO?

There is a mod I added to the game that changes the rocket launcher mesh and comes with the changed viewmesh and the lwo for the pickup, but doesn't include a worldmesh to appear in the hands of the player in 3rd person. I've done a tiny little bit using Blender 2.49 that can import and export the MD5 mesh/anim but I haven't swapped out part of a mesh before, particularly while leaving the bones intact. Since the animation would be identical along with the bones (I'm pretty sure the worldmesh only has 1 animation with a single frame as a file for the articulated figure anyway), the only real change needed is of the visible mesh. I'm wondering if anyone could coach me through doing this or assist in some way as I have not done this before? I've included a 7zip file with the worldmesh and the LWO. Thanks.

RL.7z

You need to use a program like 3d studio and do an md5export using a script like der_ton's md5export.

I can import and export from Blender. It's the rest of the process.