Hi "NLA" welcome aboard! Not often we see somebody your age joining up, it wouldn't surprise me if you're our youngest member!!
As for Mr. Baggins I'm about 99% certain Frono was taking some humorous liberties with facts to elaborate on the issue of originality. (Thus my reply).
In another thread it was asked if Guild fans like us even go so far as to look for instruments built by specific people although with Guild that's a very small percentage of instruments as that construction method was only rarely used. But I'm pretty sure that was the inspiration for Frono's joke.
However, we'll get around to answering your question seriously.
I'm not too well versed in Guild electrics but I recall past discussions about the issue pointing out that different tops need different Bigsbys and I seem to recall the current parts usually don't retro-fit.
I assume your guitar is a Corona-built (only location I saw that made the X-180) and as such it might have a lot more intrinsic value than you may realize, even more so in the 20 years you mention. So for that reason my recommendation would be preservation, "trust me on this". I wouldn't have any objection to a completely reversible mod, though, but save those original parts!
However, give it a couple of days for some folks to respond with advice, and in the meantime here's an old thread about the model in case you find out something "good to know"
Happy New Year all! Having owned more than my share of X-170's over the years, 2b's now attempting to acquire info on the former X-180 Park Avenue. Here's the facts I've learned about the X-180 Park Avenue thus far. Please feel free to add or correct to this list with X-180 factual specs or...
letstalkguild.com
I do think you're right, that the bridge would have to be replaced as well, and that may be a lot easier said than done.
Also, I suspect you may be in France? Our member
@SFIV1967 (Ralf) may be able to suggest continental sources for parts as well as things to "watch out for" when doing such a mod.
Keep us posted and we love pics!