If the staples are sunk below the top oif the luan, you can leave them.  if they stand proud of the luan, they need to be knocked down flush.  You might want to sand the seams with coarse sandpaper … maybe 80 grit … to be sure they are flush.  Any large dips, and anything on the surfaqce of the luan, will start to show through in about 6 months, and then it’s too late.  Vacuum and sweep well before layting the tile, and keep the area clean.

If you are using the thick tile, like the 1/8″ Armstrong non-peel & stick, just score it 2-3 times with a sharp knifge and it will snap cleanly.  Be sure to plan the cuts so they are covered by base … you don’t want any cuts showing.  I use one of theose large (12″) plastic speed squares for cutting vct.  It is large enough to reach all the way across the tile, and it is plenty accurate enough for the job.

And if you are going to install the tile the traditional way with spreading adhesive, don’t get in a hurry, and be sure to trowel it smooth and even.  Don’t leave any blobs of adhesive … they will either take forever to dry, or will squeeze up between the tiles.  Be sure the adhesive flashes over completely before laying tile … you actually have a very long open time once it is spread.