Depending on how things are set up (and what you have going on in your comps) it can work to make a new comp at the res you need to output, put your old comp in it, scale your old comp up, and check the “Collapse Transformations” flag. This can also make things break…
I believe that replacing any footage files (in the Project right click on the footage and choose “Replace File”) with full res sources will work (although you may run into Anchor Point issues in your comps.)
It’s usually a good idea to work in the final res from the start (even if you never RAM Preview at full res), and output proxies for the NLE if they’re doing an offline.