Well acording to ofp.cz BAS and Lavos have joined forces to make really good Hummers (the pics are awesome), Quakergamer of desert OFP released some armed hummers ages ago but i can't remeber much about them.
As for what you need to texture/model
for texturing i would say photoshop but you might get by with Paint shop pro
for modeling a good 3d modeling package and then oxygen to convert it to ofp format.