First question, are you familiar with editing .2da files already or are you starting from scratch?
You'll first need to get Fred Tetra's KotOR Tool (
http://kotortool.home.comcast.net/index.html). It will enable you to edit the .2da file format (and forgive me if you already knew this, I'm just making sure). :)
Unfortunately there's no 'easy' way of making .2da's compatible. Well, it's easy in a sense, just time consuming.
Basic premise is that you'll need to open each and every similiar .2da file included with the mods, ie - open all upcrystals.2da files together, or all the appearance.2da files together.
You'll have to scan through each and every .2da file and compare the differences (the time consuming part). If you're lucky, the mod readme file will tell which lines were changed and what to look for (I did in the Revelations Robe Mod), if not... grab a notepad (or the program) to jot down the differences.
** - Hint: always check the last lines first, more often than not that's where the changes are going to be... just not for all mods though. Checking the modela, texa, etc & modelb, texb, etc. columns are a good second choice.
I tend to use the largest (most lines) of the available .2da files and use it as my "base" .2da. Editing/Adding lines to it from the other files. Just make sure to have a backup copy of the original just in case ;)
Some things to note are that the upcrystals.2da lines are not dependant on what line (row number) the entries are on, so editing them is no sweat, just make sure the proper columns have the correct entries.
However, some appearance.2da, and especially baseitems.2da files are dependant on the row #. If you have to place the entries on a different line, you'll more than likely have to edit a .uti file somewhere in the mix. (Further details can be given if you come upon that problem).
Be sure to take advantage of the ability to right-click and copy/paste entries or entire rows if need be, it can be a real time saver. However, you can't copy & paste from one .2da file to another. It only works within the same .2da file. Luckily there's usually similiar lines you can copy so that you'll only need to change a few entries rather than the entire line.
That's really pretty much it in a nutshell, if you need more detailed instruction or are having particular problems... don't hesitate to ask. There's plenty of us here that's felt your pain and have encountered this problem (speaking from experience here ;) )
Hope that helps, even if a little bit. Let us know your progress! :D