hi
dunno where you come from,,,but i went onto
www.ebay.co.uk
and i bought ..for £1.99,,,a cd-rom,,,which the bmw dealers use,,it has all the info about all the cars[and bikes]
even lists part numbers for you to quote at a dealer
and it show u how to change your thermostat
hope this helps a little
other than that,,,,yes,use oem parts