Appending 1st field in a file into 2nd field in another file

Hi,

I've internally searched through forums for about 2+ hours. Unfortunately, with no luck. Although I've found some cases close to mine below, but didn't help so much.

Actually, I'm in short with time. So I had to post my case. Hoping that you can help.

I have 2 files,

FILE1

23444,
12333,
55578,

FILE2
8
9
8

I want to

(a) append the filed in FILE2, into 2nf field of FILE1:

23444, 8
12333, 9
55578, 8

and in other run

(b) append the filed in FILE2, into FILE1 as follows:

23444,8
12333,9
55578,8

In ADDITION & generally, can you provide me with a solution that:
extracts the "Nth" field from FILE1 into the "Mth" filed in FILE2?

Waiting for your input, with my appreciation in advance.

BR,
Ahmed