An Excel/Word Based Quoting Tool

General information for the business: Small independant door maintenance company looking for a quoting tool to deal with large volumes of quotes
Kind of development: New program from scratch
Description of every module: Hi

Hope you might be able to help me out with a little project I am working on for a friend.

The scope in short is to provide a simple way to produce a word based quote document from data extracted from Excel - much like a mail merge but a little more complicated.

How I imagine it working is like this:
In Excel, select from a list of customers (held within the sheet - possibly pulled in from an external data source but not that important)
Once the customer has been selected, the user selects from a list of possible sites associated with that customer.
Finally, a list of assets linked to that site would be presented anywhere between 1 - 50 for example ( I can confirm this detail later if needed but best to allow for this to be increased if needed). One you have a list of the assets on the screen (they are doors) the user should then be able to perhaps tick a number of boxes relating to different products being quoted for each door. I believe there would be up to 5 different options per door, some doors would need nothing, some could be anywhere between 1 and 5 of these options. Each of these options has a price associated with it which would eventually produce a quote. For example, Customer1, Site2, has 3 doors, Door 1 needs option 1,3 & 5, door 2 needs options 1,2,3,4 and door 3 needs none.

Once you have selected the appropriate options, the user has a choice or 1 or more items of Standard Text which can be added to the quote output to explain what is being quoted for.

On the press of a button either a word document Is created (possibly mail merge style) with the customers address, site details, quote options (summarized) along with some standard text and any optional text chosen previously. I say word because it would allow the user to perhaps alter the finished document before sending. It may be better to output into PDF from Excel but I feel the option to alter the finished quote would be beneficial. It has also been requested if possible that if another check box is ticked then the document would also produce a secondary page of the quote which would contain photos of each of the 1-5 options chosen so that the end customer can see what it is they were being quoted for, along with a short description to accompany each photo.

The final output document would have a company logo, quote reference (auto incremental perhaps) and look essentially like a letter.

I hope that makes sense, I am happy to try and explain this further if needed.
Description of requirements/functionality: Should allow for the final document to be altered before it is saved/sent. I would want to add a salutation, perhaps alter some of the pre-prepared text etc.
OS requirements: Windows
Extra notes: I have an idea of what I need and hopefully have described it enough above but am happy to discuss further, and entertain other options outside of what I have thought off.