First, you want to actually have a new computer ready to go. If you are experienced in computer hardware, you may want to remove some parts (such as the RAM, optical drive or hard disk). Then, sell it, give it to a friend, or dispose of it properly.
Wow, um, just wow. Anyway, did the engine crank over before replacing the computer? If so, during the process of replacing the computer did you create a problem with anti-theft or did you forget to reconnect the battery?
No, replacing a hard drive will.
Your clutch needs replacing!If automatic trans then trans needs replacing!
What do you mean he recommends replacing it? It is either defective and needs replacing or it isn't. Take it to another Toyota dealer or trusted independent and get a second opinion. A salvage computer would be another choice if it does indeed need replacing, which I would bet to be highly unlikely. Spend the money for a professional diagnostics by someone who knows what they are doing, and you will be money ahead.
More than likely the tensioner is defective and needs replacing.
(1) Spark plugs need replacing. (2) Spark plug wires need replacing. (3) Distributor cap needs replacing. (4) Injectors are dirty and need cleaning or replacing (5) Fuel filter needs replacing. (6) Fuel pump needs to be checked.
The last thing you want to do is apply grease to a timing belt. If the belt is noisy it needs replacing or the tension-er needs replacing.
A computer should not have an ignition system.
It needs replacing
Due to its age - MANY possibilities: battery needs re-charge or replacing - spark plugs need replacing - ignition wires need replacing - distributor needs replacing - fuel filter is clogged - fuel pump needs replacing. If you are handy, many of these can be done by you, if not, you will need the services of a mechanic. They ARE durable and long-lived, but the parts don't last forever.
Before you dive in and replace the computer, make sure that the computer actually needs to be replaced. More often than a defective computer the problem is a defective sensor or a bad connector plug or wire somewhere. On a 14 year old car be careful about replacing an expensive item like the computer.
With the car or truck running disconnect only the positive side of the battery ... if it stays running that means the alternator is good if it dies then it needs replacing