what should i look for to tell if the oil pump is going bad?

Oil pumps usually last the life of the engine- and yours is only 10 years old- when I rebuilt the engine on my Fiat last year I checked the tolerances on my oil pump- and it was still within specs- so I put it back in- it works great- after 40 years! More likely your problem is the switch, sender or light-

They may not have put enough oil in it, lots of variables. Make sure your close to the full line but not too close. Its a Toyota, great engineering, great dummy lights, just take your time and check it out.