I would like to know how Matthew 26:28 could be rewritten in koine
Greek (with minimal changes) to literally say "for the many".  And as
a second question, how it could be rewritten to literally say "for
all"?

The original Greek is available at
http://www.sacrednamebible.com/kjvstrongs/B40C026.htm#v28
or in a Word document, matthew2628.doc, available at
http://www.4shared.com/dir/1003173/7f552393/public.html

The answer could be put in a Word document and uploaded to
http://www.4shared.com/dir/1003173/7f552393/public.html
or it would be fine to put the answer on the Google answers site, as
long as I can read it written in Greek letters.

The new Testament is written in a version of Koine Greek.

Here's a link to a Wikipedia article:
http://en.wikipedia.org/wiki/Koine_Greek

Sorry. I misread the question. The Greek already reads 'for the many'.

Matthew 26:28 in the RSV translation reads: 'for this is my blood of
the covenant, which is poured out for many for the forgiveness of
sins.'

The Greek is:

touto gar estin to aima mou thV diaqhkhV to peri pollwn ekcunnomenon
eiV afesin amartiwn.

Neither classical nor Koine Greek has the definite article. 

The phrase 
'to peri pollwn'
('To peri pollon') means 'on account of many' or 'for many' or 'for the many'.

If you want to say 'on account of all' ie, 'for all',  then the greek is
'to peri pantwn
('To peri panton').

I hope that this helps. It's a free comment.

Oh dear. I wrote this comment in a word document, using the symbol
font for the Greek text. As you can see, it hasn't come out.
But if you paste the entire comment into a word document and
hightlight the Greek passages and put them into the symbol font, then
you should have usable Greek. Sorry about that.

Hi Amber,

Thanks for your reply, but are you sure Greek lacks a definite article?

According to this webpage, ancient and modern Greek both have the definite article:
http://www.cogsci.indiana.edu/farg/harry/lan/definart.htm

And according to this webpage, Koine Greek also has the definite
article (but lacks an indefinite article):
http://www.biblefood.com/articthe2.html

adlib

Hmmm, I was expecting Google Answers to automagically make the web
references I provided clickable.  Let's see whether html code works in
these comment boxes.

Here is <a href="http://www.cogsci.indiana.edu/farg/harry/lan/definart.htm
">the first reference</a>.

Here is <a href="http://www.biblefood.com/articthe2.html">the second reference</a>.

Here I am quoting someone else:
<blockquote>To err is human, to forgive, divine.</blockquote>

I guess not.