There is a lot more than a service with SOAP objetcs in input/output you need to understand to expose a webservice. First you need to create request/response document types which should conform to the standards. Then you need to create a wrapper service which you already have now. This would take care of wrapping/unwrapping the SOAP request/response. Here you need to understand about the XML namespaces and how IS uses them to identify the respective service for each request. Then you need to create a service to do your actuall process of xml transformation or whatever it may be. Then you need to understand the exception handling and various different methods you can do it. Note, most of these task can be performed by built-in servces.
If everything is upto the standards and goes well then you would be able to generate a WSDL in developer of you wrapper service and input/output signatures after which you can send the WSDL to the thrid party for them to consume your webservice.
Apart from the above tasks you need to know how you are going to implement the security part and understand the variuos options available.
This is just a very basic set of steps for creating a WS.
So I suggest it would be better if you could go thru these documents which have all the information you need to create, test and implement WSs. Then you can decide which is the best way to go for your requirements.
These are the docs:
"SOAP Developers Guide 65
Web Services Developers Guide 65
XML Services Developers Guide 65"
These are V65 docs, please refer the respctive docs of ur IS version. If you are stuck anywhere in understanding or implementing you can always rely on this forum for help.