Just completed this on my 94 GS last night so I will try to cover it for you... sorry, no pics.
Unless the new unit has the reservoir included you must remove the old one and install the old reservoir on the new m/c. There really is no reason to pay for a new reservoir unless yours is leaking.
1. Remove the reservoir cap and disconnect the two fluid level sensor wires. Use either a kitchen dropper (turkey baster) that you never plan to use in the kitchen again to siphon out as much fluid as you can from the reservoir or a bunch of paper towels to absorb most of it out. The prior method is much more clean and less time consuming.
2. Unbolt the brake lines one at a time with a towel underneath the m/c to catch the little bit of fluid that will leak out when you disconnect the lines. (I highly recommend a 10mm line wrench for any and all brake lines). I had two zip lock bags handy to put over the open brake lines while changing out the m/c to keep fluid from dripping on anything important. Brake fluid will remove paint like nobodyís business!
3. Remove the two 12mm nuts and lock washers holding the m/c against the booster, pull the bracket out of the way and remove the m/c. This is a good spot to note that if the rear seal on the m/c was blown, fluid has probably leaked all over the power booster and I would pay close attention to the booster. If it looks like fluid has entered the booster, you might consider switching it out as well. Fluid will more than likely cause it to fail later down the road if not done so already.
4. Take the new master cyl out of the box, remove the reservoir from the old unit by the two Philips screws inside and mount it to the new unit. Make sure the o-ring around the base of the reservoir is clean before doing so.
5. The new unit will need to be bench bled before being bolted on the car or you are in for a headache once itís installed on the car. The unit should come with two fittings that screw into the holes where the brake lines go and come with plastic tubing to connect to these fittings and run up into the reservoir that you have now filled halfway between min and max to keep from spilling. Place the unit in a vise (I didnít have access to a vise at the time and was able to do mine by holding it and placing the plunger against a firm surface to push in to bleed) and bleed the unit until no air bubbles come out. Keep an eye on the fluid level and donít let it go below the level of the hoses and let air in or you will have to start over. Once you are finished, remove the plastic tubes and install the small caps over the fittings to keep too much air from entering and the fluid from running out while you bolt it up.
6. Mount the m/c using the two 12mm nuts and lock washers but donít tighten all the way yet, just enough so it stays in place. It will need to be loose enough to allow enough play for the two brake lines to be connected. You DO NOT want to risk cross-threading those fittings or you are screwed! If they donít go in easily by handÖ stop and find out why. Remove the plastic bleeder bolts one at a time and start the brake lines into the m/c.
7. Tighten the brake lines up and then tighten the 12mm bolts on the m/c to booster. Fill the reservoir all the way up and starting at the passenger side rear wheel, remove the wheel and with a helper, bleed each wheel until air is no longer exiting the system. Sitting in the car you want to go in this order. PR
, DF, DR, PF.
8. Your helper will pump the brakes slowly three times and hold until you open and close the bleeder screw and not let off the pedal (it goes to the floor) until you have the bleeder closed. If your helper lets off the pedal while you have the bleeder open, air will be sucked back into the system and you get to start all over. Just make sure you watch the fluid level because if you run it low, you will have filled the system with air and have to start over by removing and bleeding the m/c like you did before it was installed on the car.
Hopefully I didnít miss anything and wasnít too long winded. :p