In general, it is not a full time job, so you should be able to find time for it.
Admins are expected to define the requirements of the project (project proposal), to negotiate with any applicants about the details, and to select a suitable technical writer. Then fill the application form on GSoD (deadline March 24).
If the project is accepted, admins and the community help the technical writer to get familiar with DebianEdu, if needed. The documentation project lasts for 3 to 6 months (depending on the agreement with the technical writer). Each month the admin has to fill a progress report form, evaluating the work of the technical writer so far. There is also a final evaluation, and a case study report that summaries the whole project.
If the project is accepted by GSoD, the admin should also create an Open Collective account, in order to receive the grant from GSoD and send it to the technical writer (which also should have an Open Collective account). A percentage of the grant may also go to the admin, or organization, or may be used for the expenses of the project, etc. These details should be explained in the project proposal that is submitted to GSoD.