For an Microsoft Dynamics CRM Online Instance the Webservice endpoints are located at https://<your-subdomain-orgname>.api.crm4.dynamics.com
... where crm4
also may vary with the regional datacenter your instance is hosted. (crm4 is the Europe datacenter)
Apart from that you shouldn't see any issues connecting to trial organization and running the SDK samples against it.
The username for connecting is - as you already guessed - michel@xyz.onmicrosft.com
and the address you connect to is https://xyz.api.crm4.dynamics.com