Cut it out - there may be some colour underneath.
Diode may be reverse-polarity protection - but it may also be simply acting as a fuse. Its not something I'd replace with wire however.It may be burned, but it might still be semi-functional - it can happen.If you have a magnifying glass, you may be able to make out any identifying characters (eg 1N XXXX).Final point: although you've identified the burned out diode, it'd be a good idea to make sure you've identified any underlying faults to prevent the new one going the same way.
TVS (transient Voltage Surpressor)
Looked like the (remains) of a fuse to me - some of the on board ones look like a diode (and in some cheap kit they use a forward biased diode)Bet you anything the regulator (3 legged thing next to it) is short.