Thanks for the quick replies everyone!
That's kind of what I figured - the exhaust wouldn't play a noticable part in the overall mileage nor performance of the car.
I had been looking around just for the axle-back section and think I may splurge for something along these lines:
Walker Exhaust 18561 Exhaust Muffler Muffler | eBay
Bosal 163 727 Exhaust Muffler Rear Silencer | eBay
I can tell that the car is due for a general maintenance though - replacing all fluids, filters, spark plugs, injector cleaning, etc. The car labours just momentarily when starting it cold, or when it has low fuel in the tank. I think some new parts may help out in it running efficiently and maintaining it's longevity.
Thanks again for all the level-headed advice guys
Woody