My car is an e36 and I just did the same job. Slightly different door handle. Changing the lock cylinder was pretty easy up until the point where I did something stupid. I took the cylinder out of mine using the key to depress all of the tumblers, then for some stupid reason I decided to take the key out of the cylinder. Some of the tumblers fell out and it took me an hour to put the pieces back together. The only hard part is getting the old cylinder out of the used handle. Since you don't have the key you have to use a pick to depress the tumblers to get it out. Really wasn't that hard. Just don't loose the tumblers, tape the cylinder or put grease on it or don't take the key out.