When I did mine on my st170 there was no need to remove any pipes. Undo 3 torx screws, whip out old stat, slot new one in, job jobbed. Just make sure you fit the seal on the stat before it goes in, and put a bowl or something underneath the stat housing to collect lost coolant (you will get about half a litre), stick the coolant back in the header tank, 10 minute job!