The one pieces do NOT have to be installed by a smith, but they DO have to be installed by someone who knows what they are doing and has the right tools, if you want them to be beneficial instead of something that makes your weapon unreliable/dangerous....
There is an armorers wrench that is needed for the task, and a HIGH QUALITY torque wrench, as well as a thorough understanding of what needs to be done and how to get it done....
That being understood, there is less of a point in getting these installed if they do not float the barrel (the one piece), so I suggest going that route if money is not an issue....
If you don't feel up to the job, or know you aren't, go with a smith....