That black box thing and where is the spark plugs,alternator,timing belt,spark plug wires located on a 91 - 97 toyota previa?

the black big box is where the air filter is located, for spark plugs and wires access, you have to remove the front passenger seat, the cover under carpet and the 3 bolt black plastic cover. timing chain is made of metal just like a bycicle and dont have to replace it. alternator is located on front of the van under the hood. hope it helps.