Changing the "XP required for next level" can be considered a temporary cheat, if that's all you do. It'll allow you to gain a level, but the XP required for the actual next level will be reset accordingly. Ie, if you are level 10, and you modify the XP required so you can advance a level, the XP required for next level will then show for level 12.

As for using UGE... You can do so, but with save game editors out there it hardly seems worth it. Why bother marking your XP/etc down when they'll happily tell you how much you have and then let you change it?

O.R.

I don't recommend bumping levels in short cut fashion. Levels aren't worth as much as skills are. I've been playing the game on expert and when I hit arnika (direct from the Monestary) I was "only" level 8 or so, BUT my bard had a skill of 75 in music. The reason is that the battles last longer. Longer battles means more chances to use your skills. The ONLY advantage to leveling is getting your core stats (str, int, etc...) up. Other than that, being a higher level just means that you face harder monsters.