The RS units are chassis mounted and current rating is not bad. The Mouser unit looks like they are not chassis mounted but are solder in, chassis mounted ones are $18,00 each. That's ok as the price is way less. With solder in and a diecast case you will need to drill a hole for each cap that is larger than cap, then cut a large piece of double sided copper PCB so that it covers all the openings with one piece. Drill the PCB for a snug fit when the cap is inserted and then solder each of them in (they have one solder flange). The PCB can then be screwed securely to the inside of the case which should then bond both sides of the PCB together.
The install direction is not so much electrically important but the design of the cap results in the larger part of the cap having the strongest mounting point for the cable, this should be on the outside of the case.
I could not see any current rating for the mouser caps and as they are small you may need to use 3 caps on the +5 rail and the +3v rail. Each of these rails has a number of wires in the loom so this should be easy but unfortunately costs a bit more for the extra caps of course.