http://www.atlantamx3.com/mx3scalemodel/disassembly/
Mine back at home, so I can't look at it, but I think it's a die cast metal model. Like painting anything, not just real cars, good prep definitely give the final paint a better quality, and primer for the paint to stick.
I guess it depends on how accurate you want and how much money you want to spend on this project, but neither the Presso or Az-3 are perfectly accurate.
The Eunos Presso is almost perfect, even the rims cause those that come on the SE that your b/f had, the only discrepency is the spoiler, the Presso doesn't have the spoiler on the hatch, the Az-3 does, which is the spoiler your b/f's raspberry Mx-3 would of had as well. So in a sence, you'd have to get both, and put the AZ-3 spoiler on the Presso. As well, for more accuracy, the North American Mx-3's don't have fog lights in the front bumper, when you have the body appart, you could always shave off and fill the foglight holes for a more accurate representation.
This would definitely be a tedious and you'd actually be spending $100 in model cars before even doing any of the work, but it all depends on if you want to. Mx-3 owers are usually delighted to just get the model as-is in itself since they are the only model Mx-3 in existance, ever, but the other way. it would be the more expensive way for sure, and probably not something you'll pull off in a weekend either, but in the end, you'd have an accurate and unique Mx-3 model car.