New to this sport!!

Hello all, I am looking for a new adventure for 2015 and I have the bug to do a tri. I am from northeast PA. Being 45 yrs old, my knees feel like garbage, but it could be that I wrestled for years then also coached at a local high school, not to mention that while in the service I competed in drug free bodybuilding while stationed overseas... I never used to have an issue getting into the gym, but with work, family life, and the joys of owning a home, it is hard to get in the gym without losing focus on what needs to be done before the day is over... In 2011 a group of us went to NJ to do our 1st Tough Mudder, then every year since we travel to another state to do another, most recently Las Vegas. The good thing about me signing up for races, it keeps me focused, & in shape, and ready for the events I enter...My wife, in 2013 got me into a tri, as a team, but it was a run/kayak/bike....It was fun, something different, but then she talked me into a 9 mile race on Thanksgiving in Berwick, PA, and then this past spring the Scranton 1/2 marathon...I found that I enjoy mixing up the running with something else, keeps me from being bored by longer runs, and the tri, I believe, will be my answer. I am currently training for a 1/2 marathon in Sept, and atleast 1 if not 2 more races before 2015 rings in. Now the funny thing is I race only to finish, at best I am happy to be a 9-10 minute mile guy for all my races, I still try to do my best, but regardless where I finish, I have that sense of pride of what I accomplished...(I never had the illusion that I would be known for my running ability-hahaha) Anyway, I found this site and look forward to reading and gaining as much knowledge as possible...I have A LOT to learn, and I mean A LOT... as of right now I have nothing but running shoes and a 25 X 40 inground pool, as well as a lake nearby, where the tri is held.. so I will take ANY & ALL advice you may have for me!(esp on bike selection for a person on a budget and proper gear) The(SPRINT) tri that I will be signing up for is not until next August (2015), as this year's event just finished...