if you install new software (such as chinese software) does it completely replace whatever was there before? for example the 8700c comes preloaded with some cingular stuff or the 8700g comes with a t-zones link, does all of that go away ?
thanks

Carrier specific software, like T-Zones or the Cingular browser get pushed down by the carrier. After you load new software and register the BB, these items will be pushed down over the air.

..And how do you load new software into divice/ i recently got a 8700 from cingular and i unlocked, and using t-mobile,but i would like to -tmo.software in it.

An excellent place to start would be reading the Sticky Thread FAQs at the top of the General BlackBerry Discussion forum. One of the Sticky Threads contains all the information on how to upgrade the software.

It will NOT change the branding - it will still show Cingular on it when you power it up.