I am not getting no output from peavey 16fx mixer. if i trun it off on & on i get signal for 2 sec

Take the main outputs into a stereo input (or a pair of mono inputs) on the Peavey - without knowing which Peavey I cannot tell you further info re set-up but as you'll be sending line level signal you'll need to back off the gain on the channels you input to on the Peavey

working?????

do you need the owners manual or schematics, peavey quit writing service manuals back when the deca power amps were made.

broken faders...bad muting fet on master buss, dirty insert jack on stereo buss...could be a lot of things, last drive stage to output, got hot neutral feedback on snake and blew the final stages...

you have to hit the white buttons under the window to select what mode you want the knob to select.

Sounds like a power supply failure. Unless you are adept at electroincs this is NOT a DIY repair.

It looks like using the GROUP output to drive the external FX and then bringing that back into the EFX return is about the only thing you can do in short of putting the effects after the main outputs then it would be on everything.

That's easily done. Simply connect the left(or right) output of your mixer to one of the channels on the peavey. Use any line input. Since the peavey is a mono system, there's no need sending a stereo mix to it.

Yes you can - but do not use the loudspeaker outlets on the rear panel.
There are a variety of outputs on the front panel (bottom right as you look at it).
You can use the main output,  or monitor  send - (for monitor you may need to use the relevant 'send' switches on each channel to send signal to these outputs. 
You should also turn the power amp switch to main only (not main + monitor) so that the internal power amplifier is not connected to the monitor socket
You could also use the record out RCA (phono) sockets on the Peavey to connect to the CD / tape input on the main mixer.
You can download a pdf of the manual from here for more informationhttp://www.peavey-eu.com/index.php

Quick and dirty way is to turn up one of the AUX channels, say #1 on the Guitar player's inoput channel/strip. Have all other AUX #1 completely CCW so none of the others get mixed on the AUX.

Use a TRS cable from AUX1 output to the guitar players monitor amp.

NOTE. The signal to his amp will only be controlled by the AUX1 on his channel AND the AUX1 Master.

One normally uses the AUX outputs for monitor functions.