The right Bike

Hello Triathletes,
I have been running and swiming for number of years, I had run 3 marathons and swam races of more than 5 miles long, but I am a really new on the bike
I really want to enter in this new and facinating work of the triathlon this year, but I crash with a big wall for beginers, I mean, how can I know which is the right bike for me ?
Since i know me, I know I would like to have a competitive bike even from the first race
I have been looking for an entry level bike, I do not want to affort more than $1000 this summer
The good news is I found the used bike I had been looking for, but it seems to be too big for me
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I am 5 10, and the bike is 60cm
bike sellers recomended me no bigger than 55/56cm
Please can you tell me if I could feel confortable in a trek equin0x 7 (60cm) ?

Thanks,
PS: I live 600miles from the seller of this bike, and I was unable to find any of this bike in my are bike shops to test the same bike model, seems to be a really rarely bike

Thanks again