If you look at the picture above, you can see the M1710 has a docking port, which the e1705 doesn't have.
that's true, but hopefully you won't need to replace that. The bottom part should be ths same between them all. With the exception of the docking port. so just replace the lid pieces and the palm rest and that should be it
Dell only sells the "chassis" (lower half of the laptop below the palmrest) with the case and motherboard together. Just like in the 9300/m170 series, there is one part number that includes both pieces. But this isn't a bad thing since getting both gives you the D/Dock connector. =)