Well, the schema browser's the only bit of OpenACS that has knowledge of PG internals, and there's a tradition of sorts of the PG group continuously changing internals in ways that break the scheme browser.
While that's a pity, it's not critical, and it won't affect a running system.
I'd suggest installing PG 7.4 and just trying to run your dump into it. The one problem you might run into is that PG 7.3 raised the default identifier length to a maximum of 64 rather than 32 characters (for historical reasons they're stored as char(n) not varchars) and in some modules function names were truncated at 32 chars ... which means that selects etc referencing them won't find them. That's easy to fix by simply running the CREATE FUNCTION command from the datamodel that defines the function. You might want to run your dump (just scheme, not data) into a virgin PG 7.2 instance to look for such truncations so you can fix them in your own code as well as "our" code when you restore into 7.3 or 7.4 (only functions, index name truncation and the like are harmless).
Other than that I would be surprised if you had any problem.
By leaping forward to 7.4 now you'll minimize any problems you'll have in upgrading to 7.5 when that inevitably becomes available. Since you have to move forward at least one version at the moment I suggest you at least *test* moving to PG 7.4 before ruling it out. It won't take long if all goes well.
