Hi!
No, if you use a Name Change, you don't gonna lost Change you will not lose your House or Guildhouse, it Guildhouse. It will update automatically, but if automatically. If you are invited to a house, house you will lose the access but your old name not, will not so be sure to deleted it, cuz if it. If someone create a char creates a character after the 6 months with the same name of your old name this person will could enter of the house without problem so take care with that.