For student logins, you can look at the authentication plugins included in Moodle, or look at the 3rd party modules. If none of them will work, you can write your own plugin.
For sending grades, if you want to use web services, there is the OKTech web services plugin, which provides a SOAP interface to some of Moodle's API. I don't know if it supports the functionality that you want, but it should be fairly easy to extend it if not.
If you need to hire a Moodle Developer, you can either contact a local Moodle Partner, or post in the Moodle Jobs database.