If you buy from VW, it will not be cheap but you will have peace of mind that the parts are good ones. I paid in Madrid something like 40 euros for the genuine article. Take your permisso de conducir with you so that they can relate to your serial number. They do it that way here. As for fitting it, clip in the clip on the engine side first, then the rad side. The dizzy cap can only be fitted in one way, so make sure that as you are fitting it, you cannot rotate it.
The cost of genuine leads are expensive but worth the peace of mind for no aggro. Don´t know how much though.
If you have just pulled yours apart, you may be able to repair it again.
