This process will copy Todo's, Milestones and Notes from your Basecamp project and will convert them into Tasks, Calendar Events and Notes on your new Goplan project. No data will be lost in this transition.
Step by step instructions
On goplan: Create your Goplan account if you don't have one yet
On goplan: Create a new project on goplan that will get the new data
On basecamp: Go to your Account page on the Dashboard and use the XML export function
Fill the form below and click the "Import project data" button. Rejoice!
You will get an email as soon as the import is done, which should take a couple of minutes