Size socket needed to remove a/c pulley on 98 let sabre

To work on your own vehicle, you need a basic set of wrenches and sockets, standard and metric sizes. If your asking the socket size, I don't know? I looked at the pulley on rockauto. After the bolts removed, you may need a puller to get the pulley off, I did notice a key-way on the pulley.

Serpentine belt replacement is not complicated and requires only one tool. Find the tension pulley located at the bottom of the motor. This pulley is attached to a very strong spring and holds the belt tight against the pulleys through its serpentine route around the engine. Use a socket wrench with a matching socket the same size as the hex head bolt in the center of the tension pulley. Attach the socket and set the direction to tighten the same direction the spring action allows the pulley to move. Turn the wrench handle, the pulley moves and the tension on the belt slackens. Take the belt off the pulley and let it hang. 
To install the new belt Once the belt is around the pulleys allow it to hang freely at the bottom of the engine. Again, use the socket wrench to turn the tension pulley far enough so the belt can be wrapped around the pulley. Once the belt is around the tension pulley, release the socket wrench and allow the tension pulley to take up the slack. 
Good Luck!!

Why did you not simply measure the nut size.

That is the right way, spray the bolt with some wd40 or liquid wrench.

first pop the hood and locate the water pump pulley. drain the coolant into a suitable container. there will be alot of it so get a big container.use the correct size socket and loosen the four small bolts on the pulley.DO NOT TAKE THEM ALL THE WAY OUT YET. find the tensioner pulley and put a socket on the bolt and lift the pulley to release the pressure on the fan belt and slip it off the water pump pulley.now remove the bolts from the water pump pulley. now all you have to do is remove the bolts that attach the pump to the engine block. remove the pump and clean the surface of the the engine block where the pump connects to the block. don't scratch the matting surface of the block.oh disconnect the coolant hoses that attach to the water pump.BE CAREFUL THE COOLANT WILL DRAIN OUT OF THE BLOCK AND HOSES. DOGS AND CATS ARE ATTRACTED TO THE COOLANT, IT WILL KILL THEM IF THEY DRINK IT.have fun

Typically using a 5/8" or 3/4" socket, look for the tensioner pulley, once found it will show you which way it needs to turn. Get the right socket size and a large driver or even a cheater bar for this job. Once you move the tensioner pulley out of the way, while holding it in place you can carefully remove the belt from one of the top pulleys, giving you full access to remove it completely.

If you mean can you spin the motor over by hand, yes. Just remove the drive belt and put the appropriate size socket and ratcher on the nut on the harmonic balancer pulley and use the ratchet to turn it. If you mean, can you rotate the actual position of the motor under the hood and still have a useable automobile, NO.

Find the tensioner it will be a pulley that does nothing but put tension on the belt. There should be a square hole in it. that should fit a 3/8 inch drive socket wrench or breaker bar. Use that to remove the tension from the belt and remove - do the same to install new belt

two bolts hold the power steering bracket on and come off easily. Then you can remove your bolt

You need to poke a small extension with a 13mm socket through the holes in the power steering pulley, undo it, and slide it back.