I run a marketing consultancy so might be able to point you in the right direction..here are some of my thoughts..
Firstly skills that can't be tought. Ability to work under pressure, good communication and a high standard of literacy, good proof reading skills and the ability to be organised..plus good old common sense.
I would also visit www.cim.co.uk as they run courses in marketing and are an industry body where you can develop your skills and get info.
Marketing is quite a broad brush and there are specialist areas that people can focus on...