Stopped to get fuel, shut car off & when I tried to start the car back up it turned over real slow making a clunking noise in engine-drive train? repeated to try & start twice & on the third time vehicle started like normal, & that"s when the car would not go into to overdrive

I got a reconditioned one last month

glow plug warning light on. I assume i need to replace these plugs and don't have a diagram of where they are. Do I need any special tools. I have located a glow plug kit on line with plugs and lubricant. Need some guidance.