it a little easy.
just only check admin permission (permission will grant when admin was login) and then insert or edit some row in Database
for mail function i think it maybe impossible if mail(); function was disable by host. i don't know will phpMailer work fine? so if you can use phpMailer on your host. it possible to send email via SMTP
and for user function only insert member data as new row into database.
at last for logoun button, just link to logout page and then destroy session or cookie that contain admin permission.
so, you can hire me to code that all(maybe exclude mail function). pay via paypal
so at least $40 (or $35 if you really don't have enough)
in Thai Baht it about a thousand baht. that the lowest i can accept.