If its stock now (grey motor driveline) you first of all need to decide if you want to go red or stay grey. If its red you want, then you will also need to upgrade brakes and the preferably the gearbox. This means engineers in most states. More cost, but maybe what you want.
Alternately, a nicely modded grey will sound good, go OK, protect the integrity and originality of the base car, and not cost a fortune.
I would reckon a budget of a couple/few grand would get the grey driveline going great, possibly a little more if full reconditioning was required.
To put in a red, change front end, gearbox, diff centre, floor mods, it could cost double that.
All it means is that if you want a red you'll have to be even nicer to the missus?
Mmmm, how good does the grey look now
Cheers,
Craig