2005 Bmw X3

[Bajanbmw]

I have just joined up on the board here, I am from barbados and I do hope I can get help to my question.

I have a 2005 Bmw x3 2.5i and the radiator expansion tank has a leak in it and I decided to tackle this job myself however I think I did something wrong,my bmw dealer here charged me $300us for dooing it and I hope I don't have to spend more here. On the top on the bottle I disconnected the hoses removed the bleed screw and there is a lower hose and a wire plugged to the bottom of the tank I took out,I then pulled the tank up but it seemed hard and I gived it a hard pull and it came out,now I realise the thermostat got broken and I had to go and pay $195us for a new one from my bmw dealer,so far did I do naything wrong? Next question I realised there are 2 holes at the bottom of the tank 1 big and 1 small which 1 does the thermostat go in and is there a set way to put the thermostat in like a certain end facing the ground and the other up?