> Do I have sole access in my instance as CODEJAMMER and code away happily as that user?
Yes. You have your own private HANA instance and that user basically has super user rights. You can do just about anything with it. You also have the SYSTEM user as well.
As far as tutorials, there are some in the HANA Developers Guide, in the SHINE content, and the open SAP Courses:
http://help.sap.com/hana/SAP_HANA_Developer_Guide_for_SAP_HANA_Studio_en.pdf
http://help.sap.com/hana/SAP_HANA_Interactive_Education_SHINE_en.pdf
https://open.sap.com/courses/hana1-1