Many of the Taco circulators can take a new cartridge. this means no particularly special skills or tools required. Often, a total replacement is done since for a pro, it may take about the same time, and if there's an issue, a full new one is less likely to result in a call-back later, but (in my limited experience) a cartridge replacement is supposed to replace all of the wear parts, so is pretty good fix. I haven't looked, but the instructions are probably on the www.taco-hvac.com website. If you can find them, read it, then determine if you feel competant to do it; otherwise, call a pro.
Depending on use, a circulator could die in that timeframe, but they often last longer.
The light turning on is not an absolute indication that power is actually geting to the circulator...you'd need to check the voltage. the relay could be bad. The indicator is (I think) showing the control logic's request for the relay to operate, not that it did. So, it could be the control circuits. Easy to check with a meter.