Hello and thank you for using Just Answer. My name is Chris and I will be happy to assist you.
I think I am understanding what you need to do and it can be a very difficult process. I actually had to do something like this recently for a job I was working.
Basically what you need is to create a KML, KMZ, or GeoRSS document which you could then import into google maps.
It sounds like your spread sheet has the address but you didn't say anything about it having the longitude and latitude which it needs.
One way to accomplish this is through this website:http://geocommons.com/
It will allow you to upload your spreadsheet and then you can export it to a KML which you could import directly into google maps. Full instructions can be found here:geocommons.com/help/User_Manual
Now another service which I have yet to try is this:http://batchgeo.com/
This can do the same thing by allowing you to import the spreadsheet and will create the map and then allow you to export to a KML file. It looks like they make it really easy and would be a good solution for you. Have a look at this video which easily explains batch geo http://www.youtube.com/watch?feature=player_embedded&v=nQCfoz69Bq4
Batchgeo does cost $99 for the pro version but may be worth it to you because what you are trying to do is not a simple project. It would take a long time to do all of that by hand.
It's too bad google maps does not have these features built right in but unfortunately to batch import these you will need to use another tool.
I would suggest you first try using geocommons since it's free and import your data and see how it looks on their map. If everything is acceptable export to a KML file and import that into google.
Good luck with the maps.