+0
1) Two sayings occur in the same paragraph. I feel that sounds monotone. But how to make it vivid?

2) Have I used "good thing" properly?

3) Have i used colon (:) properly?

Context:
This morning he saw his doctor, and was given a clean bill of health.

Hearing this, we immediately congratulated him, saying that was a good thing, a good news indeed. Elated, Mr.Chern looked like a child, saying, repeatedly: Yes, good news, good news indeed!
+0
(1) I've fixed that.
(2) Yes, indeed.
(3) You should quit fiddling around with colons and m-dashes, Jobb. Direct quotes are almost always executed with a comma and quotation marks. It is particularly necessary to maintain this convention as strictly as possible, because we do not want the reader to be preoccupied with interpreting the punctuation-- we want the reader to skip over the punctuation unconsciously and absorb the meaning of the direct quote itself.

Hearing this, we immediately congratulated him, saying that was a good thing, good news indeed. Elated, Mr.Chern looked like a child, exclaiming repeatedly, 'Yes, good news, good news indeed!'
Comments  
Students: Are you brave enough to let our tutors analyse your pronunciation?
Yes indeed 'exclaming' sounds more vivid. But It seems that "exclaiming" is too loud to be used there because of the limitation of original Chinese article. How about "speaking"?

Hearing this, we immediately congratulated him, saying that was a good thing, good news indeed. Elated, Mr.Chern looked like a child, speaking repeatedly, 'Yes, good news, good news indeed!'
No, 'speaking' no good-- it is not used in reported speech sentences.

If 'exclaiming' is not right for you, then you should remove the exclamation mark at the end of the expression and remove the repetition of the phrase 'good news'; 'exclaim' is the natural and correct word as it stands-- he's elated, he's repeating, and he's got an exclamation mark at the end of his exclamation--, whatever limits you may have in Chinese.
The two definitions about "exclaim" by AHD show:

1) To cry out suddenly or vehemently, as from surprise or emotion.

I think Mr.Chern didn't "cry out", just "say";

2) To express or utter (something) suddenly or vehemently.

I think he said repeatedly, not "suddenly or vehemently.

Of course, I'm not sure whether the definitions are limited.
Teachers: We supply a list of EFL job vacancies