Nominalizing Sentences
 

I'm having some difficulty understanding the difference between these two sentences:

ミルズさんはらいしゅうしゅちょうにいきます。

And

ミルズさんはしゅちょうに行くのはらいしゅうです。

Apart from the textbook stating that ...のは　is identfying everything before it as the topic of the sentence I'm in the dark.

Hope someone can help with this. Thanks for looking.

Assuming you mean 首長 (I don't know what else it could be here), something akin to:

Miles will go to the section chief next week.
vs.
(Regarding Miles going to the section chief, it is next week
or
It is next week that Miles will go to the section chief.)

Note the difference between the two, stripping all extraneous information.
First form: Miles will go.
Second form: It is next week.

I think しゅちょう is mistyping of しゅっちょう.
出張（しゅっちょう） =business trip
“出張”の検索結果（222 件）：英辞郎 on the Web：スペースアルク

Mr. Mills will go on a business trip next week.

and

The business trip Mr. Mills will go on is next week.

I don't think you can have a は before the の.

MMM has explained the difference in meaning.

　　が, not は

The は＞が mistake is the biggest mistake from a native speaker's viewpoint. You generally cannot have two は's in this kind of a short sentence.

People go on business trips at different times. The one that Mills is going on is next week.

ミルズさんがしゅっちょうにいくの is technically the same thing as a relative clause. The subject particle used inside a relative clause is always が, and never は.

Think of the second sentence this way. By adding のは to a phrase ending in a verb, you are nominalizing that phrase or in my own words, you're forming a relative clause.

ミルズさんは出張に行く (Mills goes on business trips.) is a sentence by itself.

To nominalize it, you add の to its end. Furthermore, to use the nominalized part as the subject of a sentence, you also must use は.

Now you have ミルズさんは出張に行くのは.

However, as I stated above, the subject inside the nominalization (or relative clause) MUST be が. Therefore:

ミルズさんは出張に行くのは becomes ミルズさんが出張に行くのは.

If you are the kind to rely on translation for understanding, which I personally am not, ミルズさんが出張に行くのは can be translated as:

1. the fact that Mills is going on a business trip
2. as for Mills' going on a business trip

らいしゅうです = "it is next week". Since this is about a time, you can change the "fact" part of the translation above to the "time".

I don't mean to derail but one cannot say 首長に行く even if one wanted. It's different from English.

The correct way to say that is 首長のところに（or へ）行く.

[person's name] + のところに行く
[person's title/rofession] + のところに行く

The only exception to this rule I can think of is 医者に行く, which should be treated as a set phrase.

Yeah, I was grasping at straws and didn't think there was a typo. I just forced 首長 into the sentence. :/