As Lauren has said, the Abbot is relatively easy to maintain. BUT - it's important to realise that running and looking after any tracked AFV is nowhere near the same as looking after a car. It will demand time and money to keep it going. Even if it has had the heat exchanger done (who did it and how well?) there is absolutely no guarantee that it won't go again and you'll need to lift two tonnes of engine/gearbox pack to fix it, they're a known weak point on all the FV430s. Think very carefully about what you're letting yourself in for and take someone with you who knows about the vehicle. At very least pull the gearbox dipstick, if there's any sign of "chicken soup" or froth then the heat exchanger is shot.
Out of interest, what's this one's military registration? It'll have EB in the middle, I own 08EB10.
Andy