BillyK,
There is a tech manual available for the GT275. You need to be sure that you get the correct manual for the year if I remember correctly.
I have a Gt242, GT262, and GT275 Lawn and Garden Tractors Tech manual. The part number is TM1582 (15JUL97) which replaces TM1582 (22DEC94) and TM1515 (01sept92).
The manual states that there are 2 nuts that need to be removed along with any obvious wires to the carb.
If you were looking at the carb from the side of the tractor, the 2 nuts are located a little above and to either side of the bowl.
Note: I am NOT a mechanic. Remember that gas is flammable etc.. etc...
Here is a link to a parts breakdown that you can see how it goes together.
http://jdpc.deere.com/jdpc/servlet/com.deere.u90490.partscatalog.view.servlets.HomePageServlet_Alt
Hint. Go to Print Selection on the right hand side and choose Illustration to get a bigger, clearer picture.
These nuts appear to also support the lower half of the air filter assy. Thsi woudl be the part tht the bottom of the air filter contacts.
From the picture it appears that there are then 3 gaskets.
1) between the lower part of the air filter assy and the carb
2) between the carb and a heat shield
3) between the heat shield and the engine.
It may be that the gaskets are holding your carb on and will require more effort to remove. I think that you woudl want to replace all 3 of the gaskets when reassembling.