Id get another marineland stealth heater, I have a 150w and it's never failed. You said yours was an older model, and didn't have a temp dial or light, hopefully they'll give you the newest model, instead if the older model you have.
May not have explained it right before - his heater had a temperature dial (not the old school low - medium - high) but it did not have a light to indicate whether it was on. Think it was about 18 months old but I'd noticed that the newer models of the Pro have a light on the temp dial.