Substitute specific lines with lines from another file

Hello All,

I am new to this forum. I am currently facing a problem in manipulating files.

I have two files called old-matter and new-matter

# cat old-matter

abc: this, is a, sample, entry
byi: white board, is white in color
rtz: black, board is black
qty: i tried, a lot
asd: no solutions, found for this task

abc: this is, the second, sample entry
byi: second, entry of white board
rtz: second, entry of black board
qty: second, entry of trying
asd: second, entry of no solutions

abc: this is, the third, sample entry
byi: third, entry of white board
rtz: third, entry of black board
qty: third, entry of trying
asd: third, entry of no solutions

......
......
... and so on up to 1517 entries

in this file, from the line begining with asd: to line ends with asd: is considered as one entry (or a paragraph).

now i had created another file called new-matter, which is having ONLY the first line of the above said each entries(paragraph) in the newly formatted style, as the following;

abc: newly updated, this, is a, sample, entry
abc: newly updated, this is, the second, sample entry
abc: newly updated, this is, the third, sample entry, with more info
....
....
1517 lines

Now i need to replace all the lines in the old-matter, which starts with abc: with the newly formatted abc: lines from the new-matter file. Here the critical thing, is, it should be replaced correctly (first paragraphs abc: should replace with first abc: in the new-matter and so on...), bcoz all the new entries are Uniq (this is actually an address list).

Also i need to put a blank line above all the line starts with abc:

Thanks in Advance...

dont you already have that? all the "abc" lines from new-matter are already the first lines of every paragraph from the old-matter file.

please post a snapshot of what you want as output.