三人行，必有我师(焉)

…I'm so sorry to say this but it's all context LOL.
谢谢，sigh... at least it's good to have it confirmed...

I'd take "want" as the default meaning (dialled up to "need" only if context suggests it and/or words like 一定要 are involved), and "gonna do" only if a timeframe is specified.
This is an excellent baseline to work with, thank you very much.

Though 所以邮局是要关门的 reads odd to me for reasons unclear – I'd probably use 会 here unless the holiday wasn't a regular one (literally my first thought was "what, is it closed for some national mourning" LMAO. idk)
不好意思！ Based on your explanation, maybe this ought to be 会 as another "habitual" thing, as opposed to 要 like, out of deliberate intent?