Road Bike vs Tri Bike

You can probably jump on it and ride for training and riding around. If its a huge deal, go for it and if it doesn't fit you can always resell, I can't see a 1000 costing all that much used. This is a great time of year to look around for bikes, I'd suggest keep looking around and find a bike that fits you right for the same money, unless ofcourse its crazy cheap and not much a risk to your checkbook like I said earlier. You may be slightly streched out on top depending on the geometry difference even though the seatpost lenght is ok.

I slightly oversized my first bike for a good deal, it got me through 2 seasons and I didn't regret it. Don't get a bike that can cause an awkward motion injury, make sure you're riding comfortably and safely - if I was you I'd shop around a bit more first.