4.3 doesn't break anything, it deletes the OLD hbc (unless u have SM hacks) and it stops bannerbomb
4.2 and 4.3 are no different than 4.1 (just more anti-piracy failures) so thats why no1 is bothering with 4.3
to install the shop channel, u just need to install the latest IOS56 and the latest shopping channel (v20 i think)