Hi Erin! I applaud you desire to participate more actively in the Mass. When I returned to the Church, I didn't remember what to do or say. Getting a Sunday missal (which can be found for less than $25) helped me, in that I could read ahead of time and re-read the responses. Getting a missal of your own would allow you to get comfortable with the layout of your missal and know where the responses and readings are. Plus, you'll always have it if you visit another parish.
However, if you want to spare yourself the expense, I would suggest getting to Mass early to understand the layout of the missal there. If it's the kind in which the missal is separate from the music book, it will be easy to follow along because when you get to the end of a section (the readings of the day, for example), it tells you what page to go to for the next section (i.e. the profession of faith). If it's like the one my in-laws' parish used to use, the Order of Mass is in one section, the readings are in another and the hymns in yet another section.
No matter the layout of the missal, you can take slips of paper or post-it notes as bookmarks to help you find the appropriate pages as Mass progresses. And don't be afraid to ask someone sitting near you (quietly and after they finish praying) to help you. Simply explain that you aren't Catholic (*yet :)) and want to follow along with Mass. I'm sure most people would be happy to oblige. Or you can ask one of the ushers to help you with the missal.