I'm looking for a full size oven, with or without burners on top. They didn't have any big ones at the Kfour on Monivong.

Where is the best place to look for a new or used oven in PP?

Gas or Electric ?
I bought an electric black and decker oven at sorya mall $65, (it's for sale now $40 OBO) but the aren't great but much better than nothing. Sorya mall has gas ranges around $700. The Akira shop has them (electric), i personally don't care for Akira stuff.
Aeon mall has gas oven that goes into a cabinet also some electric steam/convection/microwave/toaster combination electric ovens super expensive over $500.
I've been told there are shops around central market with Chinese gas ovens.
Took me a while but just bought nice gas range used from another expat. Lots of high end kitchen appliance shops have built in ones.

I was thinking electric because that's what I'm used to. I had some concerns that cooking with a gas oven wouldn't have consistent heat, and I'm not interested in a cheap Chinese product. Are you happy with the gas oven? Would it be cheaper to pay for gas instead of elec. power?

Yes gas is cheaper, its insulated also with double glass door that's helps make the heat even.
My electric has a rotisserie and is OK for occasional use for a chicken, cake or cookies, but usually takes twice as long as it should to cook anything.
If your just going to use it occasionally electric is OK.
I like cooking and rarely go out cuz I can make it cheaper and just the way I like at home.

This is the one I bought $270. used.
I would suggest getting an electric, because they are cheaper to buy. Use it and decide if need something more.