Users need to be able to complete an external word form

Hi All,

Our sales team have a huge form that needs to be completed before the sale can be completed. 

I have created the form in word.

1. How do I add the form to the opportunity?

2. Certain fields e.g. account name, need to auto-populate when the form is opened

3. the form needs to be saved against the opportunity.

I tried webresource, but that doesn't really work.

I tried word template but they can't complete the form and save it against the opportunity.