so i should update before i hack?but i dont know how to update using homebrew apps,i know nothing about wii's

Just look up on how to install the Homebrew Channel on 4.3
Really it should be super simple, just get a flash drive and the required files and follow instructions.
I already gave you a link to look into earlier in this thread.

Yea what Reamer87 said.
If you have a fresh wii still, just update it to the latest, then start looking into softmodding it using a tutorial for 4.3U [and nothing under, has to be the specific firmware you're on]
Whatevers required to softmod it, its definitely better having a softmodded wii, rather than a plain one. You'll just need a 2 GB SD card, or a flash drive if the tutorial requires it. as far as I know, on 4.2, you needed specific game exploits to softmod such as ssb Brawl, or lego batman. there may be other ways now adays

so i can still do the hack EVEN if i update the wii to 4.3u directly from nintendo?

Yes.