Re: Very basic powe supply question.
Writing down the locations isn't a bad idea, but if this is your first time replacing a power supply, you may forget what goes where as some connectors connect very close to each other.
If you are able, take pictures, many pictures from different perspectives.
How old is the computer/power supply?
If the power supply is not older than 7 years or so, then a modern power supply would suffice.
Using plastic twist ties should suffice. There are better options though, including tape and zip ties. I would recommend using a small amount of tape over the twist ties because it will not be conductive, and the twist ties can exert a lot of force on a small area if tied too tightly. This can shorten the functioning lifespan of the wires, same goes with over tightened zip ties. I would use zip ties or tape over twist ties.
Edit: Unimportant; The metal in twist ties is not aluminum, but an iron alloy.
Build to be updated, a reminder to myself.