Lisasha3

Hi there!
Looking to replace my current heater in my attic bedroom. I live in a ranch so upstairs bedroom is a converted attic. Room size is about 40ft x 15ft. I currently have an in the wall vented gas heater that is 1000 years old. The efficiency on it is terrible and now the pilot light goes out within 24 hours of running it. The unit is so old the gas & electric company aren't even sure how to light it, let alone fix it so I think it's time to replace it.
I'm looking for a simple option that won't break the bank. As a single mother I will not have the ability to have someone come in and do this for me start to finish so I'd like to do as much as I possibly can myself before asking for help.
Question is for the space (~500-550sq ft) what should I use?
Stay with the gas heater or swap to electric? This is the only gas needed in my home - for this one heater so it would be nice to eliminate.
But if I do go with another gas - Vented or non vented? difference?
If I swap to electric, will a 120V continue to flip the breaker? I have a small space heater now downstairs that does this constantly when on higher wattage. Will I need a dedicated breaker for this? How much of a nightmare is it to run 240V?
I was even considering 2 small wall heaters because the room is divided by a half bath, but again I don't want to have to be in the cellar flipping the breaker all the time. This would be an ideal option though because of the length of the room. Since it is a bedroom the heater will not be used much other than to maintain a low temp. I'm hardly ever up there, only to sleep and I maintain temp around 63-64 to sleep.
Thanks in advance for any feedback/help!