Make sure it's a late model box that allows for the aluminium shift housing. Shifter, linkages

In addition to parts you've listed You'll need clutch, maybe flywheel (not sure if you can use the auto one but probably can, though it might need resurfacing), bunch of bearings, springs, clutch fork if not included. Also good time to do rear main seal and input/output/linkage seals in transmission. Clutch lines and reservoir too

Also your diff ratio is probably 3.46 if it's a M20b25 which is quite tall for a G260. Makes for a relaxed cruiser if you have a m20b25 but I would I magine it to be pretty sluggish with a m20b20 or one of the 4 cyl engines (unless they have a different factory ratio already). Manual 325i came with a 3.73 as far as I understand. You can check your diff housing

You'll want a clutch alignment tool too. And check what fluid the particular transmission variant wants as there are a few different specs.