installing touchscreen in my 05 sut

[adamw89_2000]

ive been searching for countless days now and still not a direct answer to my question... i have an 05 h2 sut, no lux or adventure series.. i think... it has standard 6 disk cd player and radio. im wanting to install an aftermarket navigation/dvd/ touchscreen in it.... not sure on what model yet but what all do i have to install with the unit? my local stereo shops wont touch a hummer they said..... to much in them... i know it can be done with right adapters but what all will i need to retain my factory onstar/chimes/ and radio control functions? thanks