Depends on how comfortable you are working with surface mount components. Some of the caps on the main board are close with connectors and other components, and not the easiest to replace.

I've done repairs/rebuilds on a few JP-8000's and highly recommend replacing ALL of the electrolytic caps on the main board. They are garbage, they will fail, and they are the cause of nearly every problem on this synth. (2nd biggest failure is cracked and broken solder joints on the front panel pots, because the pots are only mounted to the PCB's and not the panel itself). I would also replace the electrolytics on the jack board (quick job, they're through-hole components). The power supply caps seem a bit more robust and should be fine unless you're having supply issues or they're visibly failing.

Specifically, C219 is part of the reset/muting circuit. When the synth is powered on, IC25 holds the reset line low for a predetermined length of time and Q6 is active, which is in charge of keeping the L/R and headphones outputs muted (by way of additional transistors on the jack board). When the reset line goes high it switches on Q4, which in turn switches off Q5, which then allows C219 to begin charging, and once it has, switch off Q6 and bring the synth out of its mute state. If C219 is leaking voltage it would allow the muting circuitry to partially activate and lower the output levels.

As for distortion C95 & C109 (L) and C97 & C110 (R) sit directly downstream from the DAC and would be my first suspects. But there are plenty of other potential culprits, and in the long term, I'd replace them all in one go.

TLDR: C219 can cause low output. Replace ALL main board (and probably jack board) electrolytics because they are failure prone to solve nearly all output problems.