I have Nokia E51 that has been in very active usage for couple of years. During this time the side buttons have worn "a bit" as shown in the photos.
The dissemble is started by removing back cover, microsd card, SIM card and the battery.
Under the front cover there was two more (T6) torx screws on the top of phone and two clips next to the battery, one on both sides. Then the mainboard of the phone can be separated from the body.
Before I put the parts back together I took some comparison picture of the old and new body and I think everyone can see the difference. :)
After cleaning the parts a bit I assembled the phone in reverse order. This whole process was in my opinion very simple and took me about 30 minutes to do.And here is one more photo of the result.