I did my first 5K last fall at the age of 59 and used the C25k program as a good base start. My biggest issue was translating the program from treadmill running to outdoor running. Nice soft tread on the machine but not so nice and soft on asphalt! Transition carefully and slowly from inside to outside. I also used my HRM to watch what my poor little heart was saying and when I saw that it was pushing a bit too much, I slowed down to a walk and then picked up the pace again. But I was so thrilled to have finished the race (not last!!) and I'm training for two 5k's in May, one in July, a biathlon (running and cycling) the end of July, and a fall 5K in September. I'm am not a runner (little troll legs!--built for cycling up mountains!) but when I was running and hearing the support from the people on the route-it was such a high. Loved it!
I thought I would be embarrassed running at my age but I realized that I was running a 5K race and those that may be watching me and judging me were sitting there doing nothing. You'll do great--remember it's your run, your pace and your achievement. Go for it!
~~AG~~