2 power supplies one breadboard

I'm back for another awful newbie question. Thanks in advance for your patience.

I'm going to build my own arduino on a breadboard for an existing pure arduino project. My arduino sketch controls a motor and fan with an external 12v power supply and 2 transistors. Other sensors plug into the breadboard and then the arduino, which is powered by a 5v usb wall wart. I'm trying to combine everything.

Early on, when i knew even less than I do now, I tried to run everything with with the 12v into the vin jack. I fried an atmega that way. So I'm scared of all things power.

Is there a way to have one wall wart to send 5v to arduino and pins and 12v to motor and fan?

a 5V wall ward is too low for an Arduino according to specs... (7-20V ) The voltage will drop a bit due to the voltageregulator ....

Ok, it's just a USB wall wart, so whatever voltage that is. The point is I want to use my 12v external to power fan and motor and arduino, but not mess up the listening sensors. Probably a dumb question but I'd love some resources to figure it out.

you can connect the 12 Volt to the power socket (so not to the Vin or the +5V pin).. The voltage regulator will handle it.

This will be a standalone atmega328 running as an arduino. So, what voltage regulator should I get? Also, will I branch out the positive pin from the 12v wall wart to the regulator AND the fan and motor? Thanks for your help.