Getting your two combo boxes to work together so that the second is dependent on the first can be accomplished using the WebAssist Dynamic Dropdowns tool. It will allow you to create a dynamic client side array for the second select list that will be filtered based on your selection from the first select list. You could do this manually also, you would need to craft the js code to create an array like this and the code to filter and populate based on the selection. If you own any of the development suites then you probably already own this tool.
The final part where you populate the other form elements based on second selection will be more custom though, you would need to make sure you have an array of all the records and values for them then filter it based on the second list.