日本語 Japanese Ask Questions Thread 5

If you have a question about the language, ask it and fellow 4channers might see it and answer it for you.

Japanese - Ask questions thread
http://dis.4chan.org/read/lang/1174719097/1-40

日語 Japanese Ask Questions Thread2 質問
http://dis.4chan.org/read/lang/1206158123/1-40

日本語 Japanese Ask Questions Thread 3
http://dis.4chan.org/read/lang/1267485093/1-40

日本語 Japanese Ask Questions Thread 4
http://dis.4chan.org/read/lang/1302350850/1-40

If I wanted to buy something from a vendor at the comic market, would it be ridiculous to say, "すみません, これが買いたいです" while pointing?   Is there a better way of doing it?

Also, is there any way to convey the message "While I appreciate your conspicuous honesty, your money has Arabic numerals on it, and I already verified that the change was correct when you counted it into your hand the first time.  There is no need to hold it up and slowly count it out again while speaking the numbers aloud in Japanese"?  I tried "いいです", but that didn't seem to get the idea across.