so your main concern is lowering the action
1. start by removing the the shims that are below the pickup. remove the saddle and pickup, and take-off the plastic shims below the pickup.
2. if the action is still too high for you, the next step is to file the UPPER part of the saddle. Yes, I said UPPER part; do not file the bottom part.. Trimming the saddle of a G-series Takamine is challenging because it has a unity under-saddle pickup. unlike conventional under-saddle pickups, you cannot file the bottom of a unity pickup to lower the action. if you do, the contact points will be ruined, and the pickup and tuner will not function.
what i actually did for mine is to completely replace the undersadle pickup (i took it out), and replaced it with a nice magnetic pickup that i connect to the preamp. this allowed me to file the bottom part of the saddle to my desired action.