L1B to H1B Change of Status

[satyam83]

Hi,
My L1B Visa is currently valid till Aug 2012.
I am thinking of asking my employer to change my visa status to H1B so that i can have my total visa duration to be 6 years in instead of 5 years in case of L1B.
I have following questions:
1.Can I do the change of status to H1B from here in US.
2.Also if my H1B gets approved when will it become effective?It is necessary that the H1B effective should start from 1st Oct?I am worried that in that case what will happen for my status after my L1B visa is expired in august.

Appreciate if these queries can be answered so that I can plan for my Change of status or go for a L1B extension.

[satyam83]

Can you pls reply??