Sprint Triathlon - where to start please?!!! VERY UNFIT!!

Evening all

I'm back for the 11th year running starting a diet in Jan and THIS is going to be the year that I actually get to target! During the hols, I was watching a programme about having a year to save your life and it was about obese people turning their life around. Long story short, one very overweight managed to do a triathlon and I thought, if she can do it so can I! It really inspired me :)

Soo... there is a mini triathlon in June and I'm going to sign up. I'm not sure where to start though as I'm pretty unfit. I used to jog about 3k in an evening but its been too muddy (and I've been too lazy!). I'm not a gym member so don't want to have to pay more than twice a week to use the pool so HELP!

Is it achievable? Has anyone done it before?

Thanks in advance