Magento Site bits

We are developing a magento website and need to add / fix the following: 1- Add order comment field to order process so customer can enter comments (for example ship next week). 2- Attach pdf invoice to order confirmation email, we have the PDF customizer, enabled to attach invoice but not attaching. Also we would to save invoice in a local folder on the server for later use. 3- Can only ship order once, for example if customer orders 5 items and we only have 3 in stock, we click on ship, changed shipped qty to 3 order updates ok, when i come back to ship the remaining 2 items, i get a message "Cannot save shipment." 4- we have ext customer attribute installed, when we add "how did you hear about us" we wont be able to edit an order, site keep asking to select this option even though it was already selected, we also wish to have this required at customer registration 5- Create an extension for customer registration form that is only required for resellers (a tick box will determine if this is required) these details should be viewable and manageable from back end. - Create a tick box at end of reg form and if ticked ask / make compulsory reseller details 6- Make tracking information a link on site (my account > Shipment), Admin and in shipping email (sent to customer). we will insert a tracking number when shipping an order, customer should be able to click on tracking number and a pop up should show the tracking information, we will provide a link for the courier, all you have to do is append the tracking number to the end. we also would like to know how to change this link in case we changed the courier int he future, preferably from Admin add a link for courier. 7- Add shelf location field for products Successful bidder is to make sure these fixes DOES NOT have any effects on any other function of the site or any conflict with other extensions.