Help on getting the meaning of a sentence.

During my visit to Japan I took the chance to buy some Japanese manga so I could learn about casual talk and vocabulary while translating them.

Although I messed up with most mangas I bought (Most of them don't even have furigana), luckly I bought some Detective Conan books, which seem great to translate as they seem to be a teen oriented manga and have lots of conversation and furigana.

It didn't take long to be stuck at a sentence: (sorry for the romaji as I don't have IME in this computer)

Ayumi: Waa! bijin da ne. Ano ohinasama.
Hibara: ee.
Conan: Soo iya, mousugu hinamatsuri ka.
Ayumi: ee na.
Genta: e?
Genta: Ayumi n chi ni mo, ii yatsu ga aru, ja nee ka!
Ayumi: e?

My problem is with the last genta's sentence, I understood each of the words, but I can't get the meaning of the sentence.

Ayumi - Name of the litle girl.
n - short form of "no".
chi - home/house (although I didn't find the chi reading on the kanji).
ni - particle.
mo - as for an negative example
ii - good.
yatsu - rude way of addressing someone who's name genta doesn't remember.
ga - particle.
aru - verb meaning exists/there is.
ja nee ka - Wasn't it?

Did I got any of those wrong?
Does ii yatsu means good person?
What is the meaning of the sentence?

Thanks for any help/pointers.

Ayumi - Name of the litle girl.
Yes, it's a female name.

n - short form of "no".
Correct.

chi - home/house (although I didn't find the chi reading on the kanji).
Correct. (there's no kanji for "chi" as it is a sort of shortened form of "uchi". It's a special form only for combined with ~no)

So it's the same as Ayumi n(o) (u)chi.

ni - particle.
Correct, it's to indicate the place in this context.

mo - as for an negative example
???
"mo" simply means "too" "also".

ii - good.
Correct.

yatsu - rude way of addressing someone who's name genta doesn't remember.
No. Here it does not adressing to someone, it refers "thing" "stuff".
As you pointed out, it sounds rather rude.

ga - particle.
aru - verb meaning exists/there is.
Correct.

ja nee ka - Wasn't it?
ja nee ka : a bit rude way of saying "ja nai ka" = "dewa nai ka".
Isnt't it? Aren't they, don't they? Have you? etc.

Hope the above helps.ﾂ

Thanks again for the help.

I've come across another thing I do not understand.

Person: Chotto, wasurechattan desu ka?
Person: Kyonen, genta-kun ga mebina o otoshite te to kubi ga orechatta no o.

Basically in the first sentence the person asks Genta if he has forgotten.
In the second sentence he continues the idea started at the first sentence:

Kyonen: Last year.
Genta-kun: Name of the subject.
ga: particle.
mebina: Female doll
o: particle.
otoshite: verb to fall.
te: hand.
to: and.
kubi: neck.
ga: particle.
orechatta: slang of the past form of the verb break.

I understand the general idea: Last year, genta broke the hand and neck of the female doll by letting it fall.

My doubt is about the two last words.
I know "no" is the possessive particle and "o" is a particle that references about the target of the verb. But what are they doing there in the end of the sentence?

The whole clause, "Kyonen, genta-kun ga mebina o otoshite te to kubi ga orechatta", is the direct object of the verb "wasurechatta". That is, the two lines make one sentence.

note:
の ＝ こと/ということ: the thing that...

君がいるのを忘れてた ＝ 君がいることを忘れてた
(This particle "の" nominalizes a verb/phrase.)