If you have attic or crawl space access then pretty easy job to run in the walls. But since you're asking the question, I'm guessing you're new to this. So do what you're comfortable doing. If you don't have a plan in your head on how to run the cable in the wall but know how you can accomplish it with surface mount then go with what you know how to do. If you don't have a game plan either way then you need to hire someone to complete the job for you.

If you know anyone that does this type of work that is more experienced then you may want to tag along with them and help them with some jobs running cable so you can get the advantage of their experience and they get help with some cable jobs, so both parties get something out of it.

When I did my first cabling job I would sent with a experienced tech, so he'd give direction and I'd do what he said. If I had questions I'd ask him. Though most of it is pretty straight forward you get comfortable with what you're doing. The only times it gets to be a pain is when you have very limited access, foam insulation, dealing with firewalls (I'm talking about construction firewalls, not networking firewalls).