it could be 180 bhp but it could be 150 bhp the 180 was available after 2001 iirc but not all 1.8T's built after that were 180 bhp, you'll have to check the sticker under the boot mat or on the options list or get the engine code.
service interval on fixed service is every 10k
no additional servicing required as the turbo pretty much looks after itself (aslong as you less her cool down before you switch the engine off)
i'll let a petrol head answer the dump valve question.