Replacing the throttle-body base gasket

What is your question?

I'm having a little bit of trouble with my Swift/Firefly/Metro. It's the 1.6 5speed sedan, and I get a bit of rough idling, throttle stumble and when I downshift, I get the "BOM-bomomomommm" noise (I have a sports exhaust fitted) that you would usually expect from a rally car or something, but I don't mind that. What I mind is that under gentle or normal acceleration, I get a stumble, as if there's a miss. I Googled it up and found out it is probably a faulty throttle-body base gasket. Is it a simple on/off operation, or is it a bastard to do? PS Not from Massey, MD. In another country.