Best cap for Sigma 17-50 2.8 lens? (also, filter and hood)

Just bought a Sigma 17-50/2.8 lens for my Canon T1i.

Frankly, I'm not even sure if this comes with a hood. But I read somewhere that install or remove the lens cap, the hood must be removed, and that it's better to buy a Tamron cap for this lens.

Anyone with any insight into this? I'd appreciate any tips.

(And, if anyone has recommendations as to whether I should add a filter to this, I'd appreciate that advice, as well as what kind of filter.)

Many thanks!