Recently replaced the power steering pump and P/S high pressure line on my 98 deville & thought I would share the experience. The pump is remarkably easy to change & could be done in a parking lot with minimal tools.

Note: there are two pumps, one for deville & other is two piece pump for commercial limos, etc. be sure to get the right one. Buy the base pump without the fluid tank & reuse your old tank. An Oring for the tank is supplied with the base pump.

Note: you will need basic tools, plus a P/S pump pulley puller. This tool is dirt cheap and serves to both remove & reinstal the pulley. A bolt, nut & big washer will also work to reinstall the pulley. Do not try to remove the pulley with a standard puller.

Pump Steps: (time to complete max 1 hour)
1/ use a 1/2" power bar or ratchet & insert it in the square hole on the idler pulley & lever the pully upward, then remove belt from P/S pulley.
2/remove the clamp from the P/S return line & pull hose off tank. Use a wrench & undo the P/S high pressure line.
3/Pump is held by only one bolt. Using a socket & extension undo the bolt that is low down BEHIND the pump, almost underneath pump on the firewall side.
4/Lift out pump by tipping it forward as the front side of pump is held in a slot.
5/Remove tank from old pump. Tank is held to pump casting by two sliders. Pry up tab & slide these off then remove tank & instal it on new pump using supplied oring. Reinstal sliders.
6/Remove the pulley from the casting using your pulley tool and reinstall it on the new casting using the same tool.
7/ Instal pump on car, attach belt, start car & top up with fluid. Bleed air by turning side to side slowly.
8/ Pat self on back for saving a fortune. Now test drive to beer store for refreshment & reward.

High Pressure Line Steps: (time max 1 1/2 hour)
This is also a no brain job but is dirty & time consumming.
1/Jack up front "DRIVERS" side of car high & block.
2/Undo line from P/S pump
3/There is a frame clamp somewhere down low on this line you must find and undo.
4/ Underneath the car on drivers side you will find the other end of this line terminates at a manifold along with several other lines. These lines are all grouped close together and in a restricted space and it seems impossible to undo. However if you are under the car on your back, feet towards the front, reach your left hand up and around to the inside of the fender well, here there is a soft plastic flap that you can reach through with a wrench. It is still a tight fit and only permits very short strokes with your wrench but it is the only way.
5/ IMPORTANT: Put a piece of tape over both ends of new line to prevent getting dirt in it while installing. Have someone feed the new line down from above while you guide it along the frame from underneath and reattach it to both ends.
6/ Start car & refill P/S tank. Bleed air by turning wheels side to side slowly. Check for leaks.

NOTE: It is always a good idea to flush lines after installing a new line or pump. Do this by disconnecting the return line from the P/S pump tank. Plug the hole in the tank. Find a chunk of hose to slide over the return hose to make it longer & stick the other end in a jar. Start car & let it run fluid out into the jar. Discard used fluid, reattach lines and refill tank & bleed air.

Cheers all! For the sake of keeping it simple, I have avoided steps and things which are common sense or readily obvious.