All good stuff, especially from GRP - except that the Arrow III doesn't have the "press or swap" gear lights of the Arrow IV (well, ours doesn't). The panel lamps trick is a regular - if you get no greens, look to see if the big red "gear unsafe" light is on. If it's not, tell the instructor to turn off the pesky panel lights and quit playing games.
Generic Arrows have more load-carrying capacity than generic -180s etc, although you'll need to check the W&B sheet for the one you fly. Ours is 1755 lbs empty, 2750 lbs MTWA; I suspect that since we had the new radio fitted we may have over 1000 lbs real payload capacity. Reweighing deferred till we have the paint job done.
BUT you will be lucky to get 130 knots cruise out of one. That's what the book says, but ours usually trues out at something around 125.
I'd reckon on a couple of hours conversion, if you get a meticulous CFI. There isn't much to it in theory, especially if you're used to CS props already, but it's nice to do all the emergency extension, uplock and when to turn it on/off, etc in comfort.
The Arrow III usually (maybe always, I dunno) has the larger (72USG/60IG) tanks, so you can make the trade-off between payload and range. Ours, with full tanks, will fly a lot further than my body can handle comfortably (even with the ANR headset). Full fuel is 462 lbs which makes quite a dent in that payload...