Yes, you'll need a tlk and 2da editor.
Besides adding your custom PrC's line to the classes.2da, you'll also have to put together it's feats 2da, I believe a skills 2da as well, and then script the abilities tied to it's special feats (unless you're just making a PrC that gets already established feats/abilities).
If you open up neverwinter explorer (also available off the vault), you could open up the resouces for either of the expansion packs, and look at one of the already established Prcs to see what other files you may need for your PrC. Then of course, you'll want to name it and label it in your custom tlk (the stringrefs are linked by row number, you'll see example of that in the classes.2da. A line for the name, again but without capitalization, one for plural, ect. Just remember that in a custom tlk file, while your editor may say line 1 on a new blank tlk, you'll want to reference the line's actual offset number. I forget what the exact number is, but your custom tlk's lines start after the default dialog.tlk's last line. So if it's something like line 120849, you would then reference line number 120850 in your 2da to use that first line in your tlk.)
