I have a 98 4Runner 3.4L. I want to change the thermostat, so I need to know where it is located. How easy is it to change, what tools would I need? I'm not a mechanic, however, I am good with my hands, if I have the proper instruction. Thanks for your help.

Block end of lower radiator hose in water inlet next to block. Socket wrench, pliers, screwdriver, drain pan for coolant is all you need.

Is there a diagram online that you know of? If not, then can you tell me if I'm underneath the car, is it the right lower one or the left lower? Or would it be obvious once I look? You very are helpful and you know sh*t. I'm trying to do certain things myself so that I can learn and save money at the same time.

If you are looking at engine from the front of your truck, the inlet is at the lower right of the engine. Read the instruction that come with new thermostat for proper orientation when putting it in. If you are getting a OEM part, remember how the old one came out and put it in with same orientation.

I bought it from the dealer and the thermostat didn't come with instructions. According to UMSAM, if I'm underneath the car it will be on my left.

Havic,
This is out of Toyota Service manual

REMOVAL
1. Drain engine coolant
2. Disconnect lower radiator hose
3. Remove thermostat
(a) Remove the 3 nuts, wire clamp, water inlet and thermostat with gasket from the water pump.
(b) Remove the gasket from the thermostat.

INSTALLATION
1. Install Thermostat
(a) Place a new gaset to the thermostat.
(b) Inall the thermostat with the jiggle valve downward.
(c) Install the water inlet with the 3 bolts.
Torque: 20 N.m (14ft.lbf)
2. Connect lower radiator hose
3. Fill the engine collant
4. Start engine and check for leaks.

Hope this helps.

Thanks.