Custom Backend

I have a certain system i need built. It would be a global administration area with certain functions contained in the one admin area such as: --form building (ability to create mulitple forms for different pages in the site like party reservations, feedback, contact forms stored in db and emailed when submitted) --newsletter admin (client sign up on front end) --news/calendar area (updated by client as needed from admin area) --specials/coupon page (post specials and coupons) I was thinking something that could be added to any page in the site via php code or something...maybe an embed option is generated after something is created like the forms, new coupon page etc... I have the design handled I just the need the backend built and want to see what prices are for something like this. Admin area would manage all of these functions via 1 login. If I am not specific enough please ask and I will try to explain more. I am familiar with php/mysql script installation so if this could be built in such a manner so that it would install similar to many php/mysql scripts i could handle the installation.