Anyone know of a plugin/mod that shows the target's level/combat stats?

I don;t know of any mod that has that but if you have the Bloodmoon of Tirbunal you can see their health.

Why do you need that what do you need to know

Open console.
Click on target.
"getlevel"
OR
"get$skillname" (for instance, "gethandtohand")

I been trying to come up with a way to do this by using the GETDETECTED function to determine if you have been seen, and then using the get level and get skill gunctions to retrieve the stats to display in the text box but the problem is that I don't know if there is anyway to identify the target so the script would know where to get the stats from.
Also this would get problematic with the message boxes always getting in the way. I think to actually add something (like the enemy health bar) you would have to edit the source code and that is well beyond my noob-like capabilities.

Oh well good luck you could always just use the console like abramul suggested

Also beond the limitations of legal modding as bethesda would have a nice big fat lawsuit for you if you moddifyed there source code (not to mention another one on the actual method of aquisition of said source code)