If your doing all of this for your first time it will be a lot of work. Your biggest problem will probably be running the power and speaker wire throughout the car (doors and firewall) or installing the head unit, but if you take your time and have all the necessary tools, then you should be able to handle it yourself.
Paying someone to do it all for you will cost hundreds of dollars (at least), so if you don't want to spend the money, and are willing to do a lot of reading walkthrus on the internet, then i would recommend doing it yourself.