aux belt, damaged engine ?.

[ledger]

The battery had been playing up on my 9-5 on Saturday, I was about 0.5 miles from home and the power steering disapeared then the temp guage went up into the red, limped home. Initially I though it was an electrical gremlin, but when I opened up the bonnet realised the aux belt had completely snapped.

Some water had sprayed out of the top of the coolant expansion tank and I needed to top it up with about 0.75l of water (much later once everything had cooled down).

It starts and runs ok, no obvious clonking noises, no emulsion on dipstick.

What are the chances I have damaged the engine, i.e. HG failure ?. Or are these units quite tough ?. Is it worth changing the oil (fully synth) and only 3k old incase it cooked ?.

thanks