Jeep grand cherokee 2000 beeps 3 times pauses and beeps three more times then says perform service.

SOURCE: perform service jeep grand cherokee 2005

Actually the newer cherokees are a little more complicated, it's not a reminder for an oil change. It is for an emssions service that should be performed according to the dealer. Here is the rest procedure

Turn ignition to on position, but do not start.
Depress brake pedal fully twice.
depress excellerator very slowly twice
Turn ignition off & that will reset the perform service indicator.
I am mechanic & we are getting frustrated because the dealers do not want to release this info to anyone, they want your money! Can you believe if you did not get them to perform the service they charge you a 1 hour shop rate??

SOURCE: 2001 jeep grand cherokee center console beeps perform service

You have to manually reset it. Press the step button until miles to service comes up, then press and hold reset.

SOURCE: 2002 Jeep Grand Cherokee Limited pre form service needs to be erased

Service Interval

When this feature is selected a service interval between 2,000 miles (3,200 km) and 6,000 miles (10 000 km) in 500 mile (800 km) increments may be selected. Pressing the STEP button when in this display will select distances between 2,000 miles (3,200 km) and 6,000 miles (10,000 km) in 500 mile (800 km) increments.

Reset Service Distance (Displays Only if Service Interval was Changed)

When this feature is selected the current accumulated service distance can be reset to the newly selected service interval. Pressing the STEP button when in this display will select "Yes" or "No."

SOURCE: How to replace headlights on 2000 Jeep Grand Cherokee

One long bolt at the top - requires a 7mm socket to remove the bolt. The light housing will pry out with a screw driver. There are three ball and socket type connectors that hold the housing in and I just pryed off the plastic housing carefully and "balls" pop out of the sockets. Finally, I was replacing the faded plastic housing and it came with a new wiring harness. It's impossible to reach the connector to use the new wiring harness that comes with the new plastic light housing. So just use the existing wiring harness with the new light assembly.

SOURCE: 2000 jeep grand cherokee 4.0 liter engine timing belt replacement

If you have the same pulley arrangement that most 4.0 engines have that pulley is an idler not a tensioner. Your power steering pump has a pivot bolt, and a slide under the pump. You adjust belt tension using the pump.