97 Jetta GT Exhaust Leak??

[busboy67]

Alright, I've got a stock (all around) 97 jetta GT 2.0, and I've got an exhaust leak, at the first connection point, near the down pipe. Before the CAT. I've not busted out the jacks to have a look at it, but i've heard of these cracking here, and needing to be replaced (i'll just weld it, not a problem)...
The leak is not huge, it's fairly small, however, i can hear it, and there's a little black soot on the rear firewall.
MY QUESTION IS THIS!

Does this exhaust leak have a connection to my gas milage? could this be setting the O2 sensor off a bit, making me have 25 MPG in the city compared to typical 28-30? Let me know.
Also, what's the best way to remove the exhause manifold? From the top or bottom, is it necessary to take off the heat sheild (on top, below throttle body)

PS, I'm car guy, so I know "car-words" however, i"m an old volkswagen guy, not an new one, so new cars are a bit more iffy to me, the technology in them, etc.

PEACE!