I am not sure if adding the extractors is going to give you much of a power increase to make much of a difference.
The cat should unbolt at both the manifold end and flange end, just use a bit of WD40 to loosen the rust build up.
As for the gear shift, below is an image of the linkage assembly. Most common are bush 2 and 9 that wear away. Also plate 5 can fall apart in side and usually cannot be fixed, but replaced. Until you have a good look, your not going to know exactly what has worn away. Some parts are still available new if need be.
Festiva Gear Shift.pdf