I rec. changing the cap becuase the 2 o-rings usually get flattened/weak by this mileage point, and the plastic lip under the lower o-ring gets brittle and easy to break off at this age as well which causes the lower o-ring to not do it's job. It's just cheap insurance at this point as it is so inexpensive. Same with the bleeder screw. It is plastic, and you know what happens to plastic in the cooling system over the years... it gets weak and brittle, kinda turns to wet cardboard when it gets really bad. The one I linked to looks to be made of aluminum vs the regular plastic ones, so if you get that one for $3.75 please let me/us know... because if it is aluminum it would be hands down the best bleeder screw option.
And m5james covered the coolant answer. The BMW coolant is phosphate free and has a different ph level than the regular green stuff due to the aluminum on steel engine construction. It keeps down corrosion on the aluminum vs the green that just protects from rust on steel. (and not as good as this stuff imo) The zerex G04 (or is it the G05?) is the only compatible option, but is about the same price as the BMW coolant anyways... and if you're ordering from the site I linked you'd might as well get it from them too for ease, as they will be shipping to you anyways.
Pelican Parts - Product Information: 82-14-1-467-704-M9