寄 包裹去 上 海 怎 么寄 ？. 去。meaning
In your examples, take 去 as to.

She went 'to' the market ("to" do some shopping): 她上街("去"买东西)'去'了 is a complete translation for the sentence, but wordy with two 去, so just dismiss any.

寄包裹去上海怎么寄: How to deliver the package "to" Shanghai

回家去: go home or go "to" the living place (no "to" as "home" is an adv here)

信寄去了没有: Have you sent the letter "to" (somebody) yet?
信寄出去了没有: Have you sent the letter "off" yet?

带他去几个旅游景点: take him "to" some tourist spots



Well, English uses different verbs for direction of actions, while in Chinese we use the same verb.

带他去上海: take him "to" Shanghai 
带他来上海: bring him "to" Shanghai

她买东西去了: she went shopping somewhere 
她买东西来了: she bought sth and brought here