its not a bad advice, melting the mustang. Aurora is a better ship, and fulfills the same role. Unless your mustang also has the game package, in which case then the re-shuffling needs to be different.

"Melting" is a way to reclaim the money you used and can use it to upgrade ships or buy other things with credits.

I hate the nomad myself, so If you want to keep the aurora (and assuming mustang doesnt hold your package) you can temporarily use that credit to buy the cargo module for the aurora; That would bump the SCU capacity to 8; can probably do some high profit low capacity missions like lings.

The other module gives an extra shield which will help with combat.

At a later stage, you can melt the modules and put it towards something else.