So you know its do- able
A lot if it is common sense like if you have an MOT coming up soon wait till afterwards 'till you do the convesion in case anything goes wrong/ so you have more time to worl on it
It may be worth picking up secondhand standard switches to work on "at your leisure" (so everything on the car still works) then when you swap out the standard ones you could sell them on - or even sell conversions/ do them to order?
If you use 12v LEDs i do not think you will need resistors
I did all my outside rear bulbs, my front sidelights, de-tangoed my indicators (chrome- orange) all my speedo/ clock binnacle and my overhead interior lights- it was a lot of work and i had no guides/ help, i bought a lot of bulbs that would not fit and are left over, i had to modify some of them (eg the pins were wrong on the tailight/ foglight bulbs and i had to file one of the pins off in each bulb )
obviously you are doing something different from that but what i mean is it probably won't be easy and it may require a lot of work/ patience etc but if you persevere.....
before, when i switched my sidelights on, it would have been 2x5w sidelights, 4x3w dash bulbs, 2x5w tail bulbs and 2x5w no. plate bulbs (total = 42w) , the LEDs would be approx 10w a massive saving
The two interior lighs were 10w each - (20w in total) this is reduced to approx 2w (i don't have footwell lights puddle lights etc it was an LX/ i only have what is absolutely nessesary ,and the interior lights stay off when i open the door (so i don't ruin my night vision)
The overall reduction in electrical load means there is less mechanical load on the alternator, so less engine power is wasted (more performance/ economy - its quite slight though ) this also means the battery charges up quicker when the lights are on .
This has enabled me to swap the 19kgs battery for a 12.5 kgs battery, for further improvements to the performance/ economy (also as part of an overall 150kgs weight-loss) - i also fitted a small solar panel, (i considered removing the alternator altogether and just running the electrics off a larger solar panel - this might work in the summer but i don't think it would work in the winter(not enough light)) and i would need a bigger, heavier solar panel and more batteries - possibly negating the advantage
Anyway, ive been through 2 winters withe the smaller battery no problems
As before, not exactly what you are doing but shows how significant the LED conversion can be