Ill post what I did many years ago (BTW i had the RTNP cd).
Install RTNP, open unrealED, edit UPak.Predator's script, replace the native functions with normal ones without any content.
Compile and save UPak.
Now copy all the contents to from RTNP to your UT, maps in /Maps/UPak instead of /Maps, to preserver tidiness and original structure.
Edit your UnrealTournament.ini, and under [Core.System], add this file path:
You may play thru the game using the original gametype, but I suggest coding a mutator that removes the intermission maps.
PD: Don't copy DLL files, don't replace duplicate files.
If UPak still doesn't load, after saving it, close and reopen Unrealed and recompile and save. Then open UPak in UT's unrealed and do the same, I remember doing some weird stuff and removed all DLL links making it compatible.