No power to the on board pre-amp tuner. Red light does not come on. Changed batteries with known good ones.

if your pretty sure its a crack in the circuit board from dropping or rough treatment then yes it can be repaired in less than an hour-contact a guitar repair center to see who does there electronics repairs they might take that on if asked , but if it just started to do this with out a known cause its most likely a component failure and that will take some time and knowledge to find cause and repair , on this unit that might not be feasible to do

What letters / numbers that appears on the screen?
If the display is normal, and you can switch to other banks, and can edit each bank, then the problem of no sound, is at the pre-amp IC input, output amp, or CODEC converter.
This is the overall image of G1X inside. Next, we zoom-in the middle of picture above.
See the next picture.
IC2 (left) is input pre-amp IC (NJM2100).
IC4 (middle) is the CODEC IC (WM8734).
IC5 (right) is the IC output (NJU7082).

Test whether the input IC is working normally, turn ON G1X, plug the guitar, go to BYPASS/TUNER menu. When the TUNER function could work, certainly input IC is not damaged.
Means only two possibilities, namely CODEC and output IC. That is not easily tested, except in specific ways.

May also, there are problems in the input / output socket.
Turn ON G1X. Try the following (see figure below):

• Test the output socket. Touch pin output socket (right red arrow) with finger / screwdriver / whatever. If sound is heard in the amplifier, the output socket is normal.
• Test the input socket, Same as above. (left red arrow). (if this happen in this point, problem is clear).

NOTES:
If lcd light are on (as you say), but appearing G1 or d5 or bt, and the system are hang / frozen, this is a different issue to the one described above,and dealt with in different ways too.

References IC datasheet:
NJM2100.
http://www.njr.com/semicon/PDF/NJM2100_E.pdf
NJU7082
http://www.datasheetarchive.com/dlmain/Datasheets-22/DSA-439015.pdf
WM8734 http://www.cirrus.com/en/pubs/proDatasheet/WM8734_v4.4.pdf
.

Is the battery installed in correct polarity? If so- try rotate it in position to rub through potential corrosion.

Since it has a remote battery, it would not hurt to look at the installation to make sure no wires are broken. Especially the ground wire to the pickup.

It might also be a good idea to apply some contact cleaner to the output plug since it is in the power circuit. Cycle the plug in and out a few times to clean the contacts. Also some contact cleaner to the preamp controls would be useful.

Be aware some lubricants may contain silicone and that can interfere with wood finishes or repairs to the finish in the future.

This is an indication of an internal component failure. The unit needs to be sent in for service. It requires special tools and skill to service.

Here is your schematic:

http://elektrotanya.com/peavey_pv-8.5c_sch.pdf/download.html

Scroll down to "get manual" and click to download. IGNORE other "download links" n the web page.

It probably has corrosion going to the battery pack, take it apart and get it resolder, at the batt

Change the battery first. It could be dying and just barely have enough power to come on at first, but not to do anything else. If that doesn't solve it, you've got a defective one and you can go exchange it.

Often, the flashing green light indicates that the tuner is NOT receiving a signal and is a warning that the tuner is turned on.

First thing is to check if you have normal output from the guitar from the pickup. If the output is normal, there MAY be a failure in the tuner.

ALSO, just because a battery is new doesn't mean the battery isn't depleted... either try another from a different batch or use a voltmeter to check it. I have seen people chasing their tails due to a brand new bad battery.

When you select the tuner does the audio OUT of the guitar cut off as it is supposed to?

i don't really know what instructions you expected, although you should have received something for the tuner and amp. I suspect that you are new to playing the guitar, as, I don't wish to sound disrespectful, you would know what to do! So first, and again I hope not to sound like I'm treating you like a dummy, plug the guitar into the tuner input. Or if It's a piezo tuner clamp it to your headstock. Most tuners are now automatic so it should pick up on the string you are striking.Repeatedly pluck the same string til the tuner changes colour, or flashes, or some other indication to tell you the string is at pitch. Repeat the above for all 6 strings.
Then plug the cable into the amp input, switch it on, and bugger about with the controls til you get a half decent sound. ( thats what the rest of us do).Don't expext too much from this package, it is budget level, but of quite good overall quality.hope this helps