On a thirteen year old vehicle, I'd be replacing every plastic and rubber component of the cooling system if they hadn't been done before. Go ahead and do the thermostat too - it's cheap insurance. Examine all your vacuum lines and fittings as well.

2002 X5 3.0 291,600 miles
2014 428i 13,000 miles

2004 325i sold at 123,600 miles
2001 525i sold at 66,000 miles