Yes, you can (and should) mention that you already have research experience (did you also do the writing yourself?). This is an appealing skill when choosing between master students who want to do their thesis project with a senior researcher. However, I would formulate it more humbly. For example, "I already have some first experience with academic writing and conducting research, so I hope this will benefit the work for the upcoming thesis project. I attached my first manuscript to give you an idea of my previous work."
Yes, it is ok to include your awards in contacting your potential supervisor. As long as it is relevant to your future work in Masters degree. It is ideal to include that in your CV in "Awards, recognition..." section and if it is a published paper you can include that in "List of Published Papers...". In your correspondence, it is good that you discuss your research interest, your past experience, and why you are interested to be in his/her group. Your potential supervisor will read your CV for sure.