I purchased this bottom of the line Fuji last summer to see if I would commit to cycling. I had a blast and bought a new bike a month ago. I would like to keep the Fuji and ride it as a second/winter/beater bike. I would love to upgrade from downtube shifters to STI. Is this possible and reasonable or is too expensive/difficult for the reward. The link below is the info on my bike that should answer any compatibility questions. Thank you for your expertise.