In regards to your original questions.... The 19's might give you a slightly rougher ride, but with that much sidewall you can play with your tire pressure to come really close. On my Q45, I went from a 215-65-15 to a 245-45-18, and both setups rode about the same.
I wouldn't expect fuel economy to drop a whole lot, maybe a little bit but overall I'd say it should be largely unnoticeable.
Handling is 99% in the tires, and going to a wider tire doesn't always mean more grip.
Regarding replica vs OEM, easiest way to find out is by seeing a picture of a known OEM wheel and compare it to whatever you're buying. In my experience most OEM brands have the brand name cast in the wheel somewhere.
Regarding refinishing, it all depends what you want done. If you have a lot of curb rash that needs to be fixed, you'll be looking at a lot more than if you just want them "freshened up".. Powdercoating can fill in some minor imperfections, but not major curb rash.
1994 Infiniti Q45- First 5-speed swapped Q45.
2007 BMW M Coupe