Don't just replace, you need to check...then if bad - then replace.
The older radios - like what you have, if nothing has been done to them, many just need a little TLC and perhaps a new cap or two - as you've suggested.
The solid state parts then can work when the older caps that would not let power flow into them - finally get powered.
As you check - use a multitester to look for voltages and you can even use the test leads as small noise injectors to help isolate the problem.
As radios age, the soldering is one of the weakest points on the board. On top of the fact that much of the Pb lead free - means the solder used is not the same as the older malleable solder using Lead.
So the low audio just might be from older weak solder joints from the wires coming off these boards onto the main PCB - even the work they have done to help interface an older non-WX board to take on the WX boards - they need some rework in the traces to "balance out" the volume levels between RX and WX - this may be one of them that needs to be re-viewed and gone over to fix bad solder traces and components repositioned on their pads on the foil side to make the radio work again.
This is from PC-66/PC-68 comparisons for WX and DSC work they had changed their layouts...
I hope this can help guide you - you'll need to take photos of the board before and after the changes so you can retrace your steps if needed.
Now, for the C29 - the WX board can be many things, up to and including a board a lot like Unidens 7 channel. Hmm - so your radio is a 1997 - so it may be a 3 or even 5 channel --- either way, just wanted to point out...
IF your radio works normally in CB side, but just has low audio on the WX side, the board also works the Squelch transistor TR12 - so if your audio drops - try grounding TR12's base - like they do here. See pin 3?
When you recap, look for WX control line (Pin 7) - it has to power the audio pipe that arrives from the WX channel selector thru a separate pin - pin 10.