This looks like .NET WCF / WSDL service, you can access it with Visual Studio but also any other WSDL client would work, but with this one you can actually access all objects, so you can properly hack it. It is created and debugged the same way:
Basically in this kind of service, you need to have SSL (HTTPS), Session (which is supported, but you need to make authentication) and Transactions (also supported).
It should not expose any objects or classes by default (in the XML you got with ?wsdl), but only login (authentication). You can wrap it in high level single object and encapsulate other methods to it, so it doesn't expose much, like getCommand().
It can also require certificate on the client side and firewall protection.
For hacking such services, there are not many useful tools, because it depends on how you code it, so you can get any WSDP / SOAP client and check it out yourself.