Hello, I'm fairly new as well so I can only be of little help to you. Sorry in advanced but it's prolly all your going to get from these forums.
The "no file or directory found" reply literally means the last command could not find the file or the folder that was specified. When that happens check the spelling first, case does matter more often than not. (so try Wl.ko and wL.ko and such) Also keep in mind that the lines just before it could be the ones that were misspelled and not actually the one that gave you the error. If that all checks out, find where the file is with dolphin (the file is "wl.ko" for you I believe) and hit shift+f4 inside that folder. This should open a command terminal in that directory for you. You then run the command again. You may actually have to restart the entire setup procedure from the beginning in that command terminal for it all to work right. It fully depends on the situation.
From what I have seen BT5 and BT4 do have enough differences that it breaks some guides and tutorials. But there seems to be enough intact knowledge that the problems are usually fixed with minor changes to them. I would try to understand what each step in the guide is trying to do rather than just entering them one by one. You may find this way that there is slight variations in how the commands work and thus how you should enter them. Also, any command usually has a “usage” response that you can access by entering -h or -help after the command. But some times it's two dashes or, like in the case of insmod, it's just the command and nothing else... just “insmod”.
Lastly, This problem is a "basic Linux use" problem and is generally frowned upon by the moderators of backtrack forums. So don't expect to much help with it here. Also, there are many other ways to do what I just told you and many different ways they could be done. So this is not a blanket “fix all” for you. More of a “point you in the right direction, I hope”. In any case, I highly suggest reading up on how to use the bash Linux command line for best results.
Hope I was helpful.