I need to find a manual for my nikkormat fs

Don't do it, you could make it worse, take it in to a camera service center.

Check to see if you locked the mirror in the up position.

The battery compartment is inside the mirror box, on the lower side. To change the battery, remove the lens, lock up the mirror, then push the lid to the left and lift it up.

You can download a copy of the manual from
http://butkus.org/chinon/nikon/nikkormat_el/nikkormat_el.htm

Take off the lens and lock up the mirror. There you will find the battery. Google is your friend

One possible source is http://www.batteriesplus.com/products/563-0/7529-Film-Camera-Battery/47473-Nikon/Nikkormat-EL/1.aspx

1) Clean the battery contacts and put fresh battery.
2) Open the top cover and clean the meter switch ( located and the wind cam )
3) Meter needle maybe stuck at the rest position. Remove the stopper and replace or clean.
4) If none of these help, check the meter cells and resistor band under the shutter dial behind the lens mount ( hard to do.)

Try ebay. Search on Nikon CS-11 .

They don't any now but keep trying. Two were listed for $5.99 last month with no takers.

Maybe because the manual authors assumed the reader would use the built in flash instead of the one you slide into the top which is ok with lens hood.

I have a Nikkormat FT, and I can assure you that there is no "timer" button on this camera. There is, however, a timer lever to the left of the lens if you are looking at the front of the camera. As for the light meter, have you tried moving the film advance lever to the "cocked" position, since that turns on the meter.

Yes, the battery will operate the camera, Silver oxides are likely only available at a true photo store.