Just decided to do this Tri Thing

Turning 40 in December and have decided to try a Triathlon.  I ride bikes everyday and can knock out a century.  Last week I tried a 50 mile ride and 2 mile run/20 mile ride and 3.6 miles.  Managed no problem but a little sore – I am still a big boy 42” waist.  I am training for a Sprint next spring and would like to work up to an Olympic.  I need help developing a training outline.  6'2" 270 (I do not weight myself - I wrestled in college and high school and do not want to follow that trap again)  I can do the ride and run but want to finish respectably.  Can anyone offer any suggestions?  I have recently warded off all of the Carbs and started to restrict grains and processed sugar.  I imagine that is why I have not dropped more weight since getting back to riding – sold my dirtbikes and invested in bicycles.