I just did this a few weeks ago. Ordered the parts from our host. My car is an '88 Carrera but I would guess the proceedure is similar for the SC.
Heating the nuts is a MUST. Get them good and hot, my experience was that the residual PB Blaster oil on the lines at least 1/2" to 3/4" from the nut should start to evaporate (as in smoke). About 3-4 minutes with a propane tourch, moving it around to all sides of the nut. Make sure you counter hold the nuts on the hard line and the thermostat when you loosen.
I was also going to do some maintenance on the front oil cooler and thought that I would drop the entire assembly but the torsion bar housing would not let me, so I had to remove the rear lines separately. I applied PB Blaster the night before, but in reality it is the HEAT that really works to loosen the nuts.
Drain all the oil, if you use these same tools you might as well remove the rear of the rubber S-line now too (you'll see why).
I did not have the special tools so these were my weapons of choice (thats a 24" long level for reference):
1-7/16 box wrench, 30mm spanner/box, Big Channel-Loc, pipe wrench
Start at the rear hard line. Heat well, use 30mm spanner on the hard line to hold it and the pipe wrench on the nut.
Photo of disconneted oil line at hard line (S-Line still connected).
Then move to the oil tank line. I used the pipe wrench here. There is no nut to counter hold so heat very well (I had visions of the fitting shearing off the tank). You will have to move the lower fender support rod (if you have one) out of the way, remove the bottom nut and loosen the upper bracket nuts and the support rod will rotate.
Disconnected oil tank line with bracket moved.
Now it gets tricky. I had removed the rear oil line supports in the rear wheel well. I had also removed the rocker panels and loosened the oil line brackets all the way to the front wheel well, anticipating removal as a unit. At the least you have to remove the rockers to allow access to the thermostat (see photos below). Loosening the hard lines all the way to the front wheel well allowed movement of the oil thermostat to get a better grip on it I thought. Your results may vary.
Start with the outer thermostat connection. This is the method I used. Slip the 1-7/16" box wrench over the rear disconnected end of the oil line. This is why you have to dissconnect the S-Line. Slide the wrench near to the thermostat nut. HEAT the nut as described. Reach thru the torsion bar access (why you removed the rocker panel) and get a good grip on the theromostat with the Channel-Loc. Slide the box wrench on the nut and apply elbow grease. Keep your chin out of the way at his point! Mine is still brused. The photo here is before I actually did the deed. The later photos show tape applied to protect the panel edges. Apply as shown and around the edge of the torsion bar access.
Close-up of process:
Same drill with inner oil line nut. Notice tape in this pic AND the plastic cap to protect thermostat threads.
Installation is the reverse. Here are a few tips to help:
Apply anti sieze to threads, but keep it off the mating surfaces of the fittings.
Also apply anti sieze to the back side of the ridge where the nut will press and (using a tooth pick or similar "tool") get the anti sieze between the nut and the fitting at the rubber hose end. The reason for this is that when you tighten up the nuts the oil line will want to twist and they will not line up or mount correctly. the anti-sieze allows the nut to turn without twisting the line. Trust me you will thank me for this one:-)
Apply anti-sieze here:
And here:
Move the nut up and down and twist it to get the anti-sieze worked into the ridge.
All done!
Good Luck
Andrew