原本ge合約內容改左...需唔需要重簽一張新ge合約呀?

In the sense of contract law, a contract will be successfully formed when the following elements are all met, they are "offer", "acceptance", "consideration" and "intention to create legal relations". In such your case, offer and acceptance surely has been made, and by written contract, no consideration is needed. Moreover, your relationship with that company is in a commercial relationship, so there is an intention to create legal relations.Accordingly, the Contract was formed. Any of the party who breach the terms or conditions is said to breach the contract.You are definitely not oblige to sign another written contract UNLESS the terms of the former contract includes something like "Subject to further changes". So i suggest you to read carefully of the former contract.If really in this case, you may have to sign another contract.On the other side if didnt include, you are not obliged to sign another contract. And if you reject to sign, you wont need to compensate the $1000.What i said above is just a really really basic. May not be that clear. You better ask for legal advice.
P.S. There are many cases about contract law, those cases are not included in this comment.

勞工法例規定：僱主更改合約內容需清楚向僱員交代，須要得到僱員同意，否則合約即屬無效；
所以僱員有權拒絕簽新約，無需賠償。

改左合約任何條款都需要取消之前果份再重新簽, 連到職日都改左就一定要保障番您自己, 因為事實上您3月係無番過工。

您唔同意當然可以唔簽, 而佢唔比您 3月番工係佢單方面更改左合約條款, 佢毀約就佢賠比您先啱。

您唔想番新時間即係雙方未達成協議, 建議您盡快同公司傾番 + 無條件取消已簽左3月開工果份合約, 佢要列明理由係公司改左合約條款, 而唔係您辭職。 您自己小心d合約/ 口頭比人捉字失。

談判期間唔清楚嘅野可以即時電聯勞工處問, 公司無權阻止。