Please provide me with your valuable inputs.

Hello, I am a software engineer and need one help from senior members. To make it concise for applying visa to Australia I need to show 10 years of experience in field of IT, I am having experience letter for 9 years from a reputed company so no problem there, the problem is with first one year of my experience. I worked in a small company(2004-2005) which was having a torturous environment and extremely bad management, when I left from there they did not gave me relieving letter and also threatened me with FIR if I joined new company without serving a proper notice period (which of course was only a false threat as I discussed with some friends). So anyway I joined this new company and did not heard from previous company again. Now after 9 years of leaving my first company I searched all the documents and found out that i have a letter from my first company that "I am working as developer there and letter is issued to me for phone connection", I can easily make some modifications in the letter and use it as an experience certificate. The content of the letter will be true to each point... My question is content of the letter is true but there is a slight bit of forgery here though 90% of chances are that that letter may not be used by Australia for verification purpose, at most they will call the company for verification purpose. Need your suggestion here - what is the worst possible scenario here if verification goes to my company and manager says that yes content of the letter is true but letter is fake (can this company take any kind of action against me?). Though I am 100% sure that company never took record of any letter they issued. Thanks and Regards