Yes, for the dash, you must remove the wood trim first. To do so, you will have to remove the radio and the tach and glove box to excess the tumb nuts that holds down the wood trim Little fingers will help. There are three on each side of the two piece wood trim. The three nuts on the right side can be worked thru the glove box hole and the radio hole. The left side you will go thru the tech hole for two of them, and the radio hole for the third. Once you get the trim out, you will see phillips head screws holding down the top dash moldings, and the speedo and tach cover molding. Also there are screws along the bottom of dash molding too that needs a phillips screwdriver.
Now pending on what model SL you have, assume 280SL, you would pull gently the old leather from the moldings. Molding will have MB-Tex onder the leather. leave the MB-Tex in place, this is for padding. Cut you new leather from the old, using the old as a pattern. I use 3M trim glue (super) for the glue. It works well from a spray can.
Now for the boot leather, Easy to bend carefully the tabs that hold dowm leather trim. These tabs are located on the under side of the boot top. Again, use the old leather as a pattern. Hardest thing to do with both the boot cover and the dash board top cover is stritching the leather around the bends/curves. You can put heat to the leather to help the process, of wet it at those corners. Can't do this fast, took me a day or two to make sure I have no winkles.
Let me know how you do, and feel free to ask me any questions.
Bob