I am not the one doing the removal- I have a friend who is doing a favor for his brother-in-law to save him some $ on labor. He recently removed the transmission from his Silverado to have it rebuilt and thought the Envoy would be similar enough. He has followed the procedure in the Haynes manual, but can't get the bell housing to break loose from the engine. He asked me for advice because I do most of the work on my TB, however (knock on wood) I have never had to touch the transmission on my truck.
No recessed bolts but the engine and transmission have to be lowered to allow enough room to get at the top ones. Really tight space there. And I just checked the manual, there re 11 bolts. 7 on the engine block and 4 in the oil pan.