A few more recommendations:
You might want to carry in a couple of bottles of liquor with you (especially if you are into good quality scotch/vodka/rum).
They are very expensive when bought from the local shops in Bombay.
If you are going to be there during the Monsoon - make sure that you rent a 4x4 with a driver and head out for a drive in the rain. Bombay monsoons are something else and have to be experienced. And you have to eat some grilled corn on the cob during the monsoons - it is the local thing.. and the corn tastes awesome.
Approach it with an open mind (don't let the dust/grime/heat and crowd bother you too much) and trust me you will really enjoy the place..