When the MAF sensor died on my 104 engine the symptoms were pretty obvious. Engine hunting between 400 and 1200 rpm in drive and in idle as well.
Wait for the symptoms to appear, why spend the money needlessly. However if you already ordered the part as might as well keep it sooner or later it probably will go. Changing it is probably one of the easiest maintenance procedure, right up there with changing the airfilter, at least on the 104 engine. Good luck.