Your question is putting the cart before the horse, so to speak. SOA is an architectural theme to make already implemented services available in a neutral format to consumers (where consumer is some other IT process). In your case, if you have CRM services already in place, you might allow your clients to connect, and implement your internal processes to make use of the same interfaces. In other words, you might want to have some service created before you jump into the SOA soup.
I would recommend that you research the business value your effort is going to bring… for e.g. Say you have a legacy CRM system that employees have to dial into the VPN to use, or perhaps take daily reports on opportunities and go over them manually… The least the new system should be able to do is to allow you to expose a web application that can help the sales people do the same job in shorter amount of time or automatically receive notifications of new opportunities etc.
SOA is only a way to think about your applications and the way the interact with other business processes outside it so that they can work in concert. Now if doing that doesnt gain any business value I’d say you already have a good system or you need to think about the problem differently. SOA for SOA sake is not going to give you your moneys worth.