七叶草,晚上好。

1. 我要休一天班，从语法上讲：

I woulk like to take a day off. 或者 I'm going to take a day off tomorrow. 都可以。

" I am taking a day off tomorrow", 从语法上讲，有点不妥，因为是"tomorrow"，最好用将来时" be going to" 来表达，所以用"I am going to take a day off tomorrow" 更好。不过，在口语里，说“I'm taking a day off tomorrow.” 也可以接受的。　

2. 如果你要用礼貌的方式表达“想休一天班”，最好说出休一天班的原因，比如：

Mr.../ Ms..., is it OK/alright for me take a day off tomorrow because I ...?

Mr... /Ms...., I wonder if I could have a day off tomorrow? Because I...

Mr... /Ms..., do you think it might be possible for me to have a day tomorrow? Because 1...

以上是我个人浅见，也不知道是否回答了你的问题，仅供参考。