There are many things you can do to try to improve your score, but most won't be a 'quick fix'. And if a company tells you they can help you with that, it's not true! For the most part, things will stay on your record for 7 years, but visit a .gov site to verify!
Also, if you are interested in buying, I would recommend Julie Tibbets at Service First Federal Credit Union. I have been a Realtor in the Sioux Falls and surrounding areas for over 16 years and all of my clients seemed to like her best!
Hope that helps and let me know if you have anymore questions I can answer for you!