All assault remakes have been remade from scratch, and if you can't remake a map like assault (which is as basic as they get in terms of bad mapping), then you shouldn't be allowed near a decompiler, decompiling a map causes the brushes to be split, and then you have to repair them, and then you spend weeks, and months, just getting it back to it's original condition, and then you have to start modifying it.
So if I was you, I'd quit the decompiling idea.
If you want to play around with assault you can have a copy of cs_junlge_assault.rmf to look at/edit/claim as your own in Hammer.
PS, claim it and die.