Back with another problem

My car tends to over heat if left running for to long i have now realised that it is because my fan is not coming on atall is there anything i can check to try and find where the problem is my maf sensor has also gone which will be replaced end of the month ( found 1 on ebay for £40 is it worth getting or am i better of going to vw ?)
Any help highly appreciated

:grin