The gear shift indicator bulb, is difficult to get at and requires some disassembly of the items around it and a little force to split the indicator part.
I used a w5w side light type led which is 12volt, having one spare and finding I could make it fit into the hole the OE holder came out from with a little heat shrink.
Wiring wise, I had already have under dash centre console led which are 3mm rind type, with resistors, so they are all powered from an ignition switches feed.
You could take the feed from the back of the Aux socket that follows ignition switching or use an add a fuse on the Aux power fuse at the glove box.
my setup involves the Aux socket power, ignition switch, switching a relay which I turn provides power to a Aux fuse box to supply my accessories. All the cables are suitably size for current current rating.