Im assuming its not the GT trim, if thats the case then it has the 1zz-fe engine from toyota. Pretty decent and reliable unit. Doesnt seem to have a sludge history/issue. You would do well getting another opinion. Maybe ask around for a reputed shop/recommendations from your friends/relatives.
Also in the meantime, if your motor is developing a sludge issue, with this heat spell, it definitely would not hurt to run a high detergent oil. 10w30 weight dual rated HDEOs are available pretty easily. Take your pick from Delo 10w30, Rotella T5 10w30 or if you are feeling spendy , Pennzoil Ultra has a very nice does of Calcium to help with the cleaning. If you have a Meijer near you, they have Maxlife full syn for 25 USD everyday, another cleaner oil.
In my experience, MMO hasnt done much to clean sludge, it does remove varnish though. It wont really do anything that a high detergent oil wont in this application. Just make sure you get a good oil filter to catch all that will get dislodged.