I know this has been covered before so my apologies to discuss this again

I am on HSMP visa and my first extension is due in June 2010. I had my child born here in the UK in may 09. I didnt apply for the visa because I never had any plans to take him out UK before my extension is due, but now I have to visit Pakistan in 40 days time
my questions are
A) What visa do I apply for what forms should I use? considering that now they have this Tier 1 visa to replace HSMP
B) What documents do I need to send for my kid's visa?
C) What is the fee?
and D) How long does the process take?
I've read similar cases here but it's confusing because everyone is saying the different thing, plus some cases were done before the introduction of Tier 1
Any help would be much appreciated
Thanks in advance
Irfan