Installing rear speakers in '05 Fabia Estate (Bohemia)

Hi all,

I have an '05 Fabia Bohemia Estate. I'd like to put speakers in the rear under the grilles either side of the the parcel shelf. I've read that Pioneer TS-1001i or TS-1002i will fit: http://www.pioneer.eu/uk/products/car_accessories/Skoda/Fabia/09_1999/speakers.html

I've been wanting to do this for ages, since having children, just so my wife an I can fade their music to the back of the car so we can still talk on long car journeys. I'm not looking for audiophile quality. I'm pretty handy, but with my car have only attempted (successfully) replacing the HU and front and component speakers a few years ago. This time round I'm guessing I'll need to take off a fair bit more trim. Can anyone advise me on how I can do the following:

1. Access the areas under the grilles
2. Route wiring from these areas to the front of the car (I'm assuming it'll be via the door sills)
3. Get the wiring to the rear of the HU

Also, I do have a pretty decent range of home tools (incl. wire cutters, crimping tool), but don't have any specialist tools. I've read you can get plastic trim tools. Are these worth getting? Anything else you think I might need beyond buying the speakers and the cable?

Thanks