lol, I always click on these topics thinking, sure, I'll tell him how to do it. Then someone does a post like yours & reminds me that people at least need to make a minimal effort to find the answer before posting.
But anyway, since I'm here & replying, I'll give a hint
I do it in the following way: Open up Fle-ids, select NameResources.dll, type in the name of the ship I want to edit, search for it, copy the corresponding ids name or info number to Window's clipboard, open up shiparch.ini in the uhh...forgot the directory... it's somewhere within the freelancer directory tree though...lol. Once open, do a search for that ids name number that you copied to the clipboard, and the search function should take you right to the correct entry.
Alternatively, you could just open up the shiparch.ini file and take a stab at guessing which nickname denotes the ship you want to change...they're not too difficult if you think about them, but I hate thinking, so I take the fool-proof FLE-ids approach.