What you are asking for is a UI modification. LOTRO currently only allows UI skinning and repositioning of already existing UI elements.
To know the range of a target, simply have the target selected and look at any skill with a range and look for it's out of range icon. Once the skill is within range then you are less then that distance form the target.
![](http://1zq5mq.blu.livefilestore.com/y1pQcydns-JcXg1AYiEeG2kZv8nLgkxjh6OzQss4A99-pTmUSATUHwsP8sDRkpZrbbDB8IdkGMo2LQ/Port_Baratan.jpg)