Integration of Java product into SAP CRM stack ABAP

Hello,

sorry if I ask very basic questions but

my company is in its 1st. year using SAP CRM, so any help will be useful.

I have been assigned the task of integration of a Digital Signature product made in Java by a vendor

into our already customized SAP CRM process.

Here are some of the system data:

current product version:

SAP CRM 7.0 / NW7.01

sap BBPCRM:

SAP CRM ABAP Server Component SAP CRM ABAP 7.01

This last data I think refers to the ABAP stack,

I have the following questions:

¿What language should we use to make this integration: Abap, Web Dynpro, Java, ? I mean the vendor even suggests .Net, PHP, ASP ,C #,

¿What transacction should we use to start the development?

¿Any link that refers to a similar integration?

Please help,

regards

Gabriel