No worries J.R., we are always happy to help, and custom ideas like this are what I really like. It tells me that people still think outside the box.
As far as brushed or brushless, it is a balancing act. Right now, you already have everything setup to run a brushed setup and you know the plane flies. If you go brushless, you may well add weight to the plane since (and I'm only guessing here) the brushed ESC is built into the receiver board or otherwise can't be removed. Correct me if I'm wrong here. So you will have the brushed ESC AND the brushless ESC(s). However, with that said, you will usually gain a little power with the brushless setup and you have more options on KV, or Rpm Per Volt on the brushless motors. Longevity of brushless motors is also a plus since the only thing you need to do is keep the inside clean and the bearings oiled.
Saving money, In the long run it can. But up front it is going to cost you quite a bit of money to get everything working. Those brushless motors are almost $25/ea, so you are looking at $100 just for the motors. You still need the ESC(s) to power them, the Y harness for the receiver if you use 4 ESC's and the props to make it work.
As for what size ESC you need, that will depend on your setup and at this time, there is no way I can know what that number will be. If you are using an ESC per motor, then you just need to match that ESC to the motor. If you are going to run a single ESC, then you need to add up all 4 motors together and then use that number to get your ESC. Don't forget, you will also need to match your battery to what the motor is wanting to draw as well. Below is a video explaining Matching Motor, Battery & ESC to help this just a bit. And, I even did it on an airplane, kind of lol. This is humorous if you know me, I'm mainly a helicopter guy.
As for props, that will depend on what you can find for the motor you choose. Make sure you can get the correct props before purchasing a motor so you don't waste money on motors you can't use.
What video did you see that brought you over here?