We use PerfectAudience for all of our own campaigns and our clients campaigns. They're a good all purpose network with lots of flexibility, great prices, comprehensive support, and once you know where everything's at it's quite easy to use.
If you're looking for step-by-step videos, both PerfectAudience and SiteScout have incredible free training available on their sites for the technical steps to setting up a retargeting campaign.
On top of that I've compiled some of the best retargeting videos on Youtube.
If you're looking for someone to do it for you, that's what my company does. You can get a quote here.