Gday andrew. I think the g69 is a good engine. Plenty of cubes to start with, also mivec i think.
imo, id keep my eyes out for a manual version of same car and buy it and sell yours. If its less than $1k change over, id say its worth it rather than fluffing around with changing it all over.
as a small example- i changed a auto tn magna to manual (and added efi and cruise and elite interior). Right up the top near the windscreen, on the firewall, inside the car, was a clutch pedal frame mount. It is welded onto firewall before painting on manual cars and its not there on auto cars. To put this mount in requires the dash stripped out down to a bare firewall and the insulation removed inside engine bay (master cylinder/booster removed and wiring as well) its a huge job for just that mount. Rediculous!
Anyway, if you are insisting to do conversion on your car, i suggest you buy a whole smashed car and swap all you need to it. That way, you have all the bits required for the job and all infront of you.
welcome