I bought mine directly from FrontRunner for about US$1300 delivered - their price has increased since then. They are out of stock now, so if you need something right away, better look elsewhere.
Here is a link that works to the install instructions (I went to the FrontRunner sight and clicked on the "Install" tab to find them - not hard to find):
Toyota Land Cruiser 200 Series Drawer Kit - by Front Runner
A total shipping weight, which includes boxing and strapping to a pallet, of about 170 pounds sounds right. Installed weight is probably around 120 pounds, but I didn't weigh them. I don't believe the ARB drawers are any lighter - probably heavier.
The space between the drawers and the second row seats is quite handy - I use it for "soft" gear like recovery straps, ground cloths, soft shackles, etc. If you want to mount "heavy" or "Hard" gear there, you would be limited by the width of the drawers and the space between the wheel wells - 37 inches. I'd suggest installing a bar secured by each of the angle iron supports at each side of the drawers and mounting to that, the back panel is tooo thin, IMO, to support anything on its own.
The drawers are not designed to be removed. They come installed and when I asked FrontRunner the same question, they said they are not removeable. With two people, after the third row seats are removed, the entire install could be done in an hour. I expect removal could be done in about the same time. To remove the trim kit, just remove 4 bolts that hold the "wings" in place and four screws that hold the metal trim plates at the back - probably about 10 minutes. Unhitching the drawer assembly is also simple - see install instructions. The unit is unweildy, even with two people, so I don't want to give the impression that these can be installed/removed at will whenever desired - they can, but it is a bit of bother to do it.
I'm still very well pleased with the drawers and appreciate the extra height of the drawers compared to the ARB unit.
HTH
ETA: Maybe a more direct link:
http://dealers.frontrunner.co.za/api/getResource/fittingInstructions/SSDS103?download=false