I removed mine not too long ago, but it was boned. Its an easy job to strip it out, slightly trickier to strip it down, I cleaned the copper contacts but it was way past its best. I managed to get a refurbed one for £40.
If you're going to do it yourself - which won't do you any harm, jack the engine ever so slightly from the gearbox, you only need to support the weight of the engine. Get an 8mm XYZ key or allen key depending on the year of the car and remove the two long bolts that pass through the gearbox, starter and engine mount, then the shorter third 17mm bolt. Now these are removed you can pull the starter motor out. With it removed, clamp the bracket section into a vice then remove the three screws supporting the solenoid, remove the +ve braided wire and extract the solenoid. Remove the two small + screws and take off the end cap, there should be a couple of washers and retaining clip, remove these. This bit is tricky, where the pinion is there is a circlip which is hidden by a tapered ring. If you put a socket over the end of the shaft and tap gently (13mm I think) it will slide down. Then pop off the circlip. Return to the other side again and remove the two long flat blade bolts. The whole casing can come apart into three sections now, but you only really need to take the end casing off unless you are replacing the solenoid lever. Remove the end casing carefully and you'll see the plate with the copper bushes attached, on two bushes you'll need to lever the retaining spring back and extract the bush. I think the min length is 8mm - but don't hold me to that. Replace or clean as appropriate. On the armature where you'll see tonnes of copper contacts, sand these with a light grade of wet and dry. 400+ grit. Then clean it up with some meth/parafin etc. Re-assembly is the reverse of removal.
To finish off, you'll need to replace the bush inside the bell housing that supports the shaft on the motor. Its a copper ring, I removed mine using a screw type stud extractor and it didn't take long, but you could also use a tap to grip it and pull it out. Pop a new one in - I did it with a 13mm bolt with a nut and washer halfway up.
Bolt it back up and with a bit of luck it will work perfect and only cost you about £15 in parts. Failing that if you opt out and want a new/refurbed one give Manchester Auto Electrical a call and they could probably post one out on an exchange basis with your current one.
