Use to get the strip from the window shops. Now you may need to hunt down one that has been around for a long time since they don't mount many auto windows like that any more.
As far as paying someone or doing it yourself - it's always your choice. There is little I will not do myself but I'm cheap and don't mind messing up a few times in an effort to learn and the reward of being able to say I did that myself.
Doesn't always work out well, of course, and not the path for everyone.
Might be simple - though not easy
Have never done a rear quarter window yet