Is this your first kit (as opposed to ARTF)? Or is it your first rc plane? If the second, the Laser 3D is not suitable to learn to fly on.

If your first kit, perhaps you should ask in the Kit Building forum for more advice.

As for your questions:

As far as I know, Irvines are designed to run on low nitro fuel (0 - 5%) so splashing out on 15% is unnecessary.

As for pipe, best for this would be the throttle pipe, though you shouldn't need one. This then gets you back to Archie and Island hobbies as they have the deal with the pipe, though Just Engine sell them as well and may be able to do something for you. Weston UK will sell them separately too (but not the Irvines).

As long as the hard wood table is flat, that should be fine for most of the work. Laser models are supposed to be very well designed and cut, so you should not need to do much work in assembling it.

The Tpins are for things like the tail plane and fin, as you usually build these flat on the board over the plan before putting in the plane. Also the wing may need the pins to ensure that the ribs are in the right place as you build it.

You also need something to stick the pins in. I use cork boards which I got from B+Q. I think they were floor tiles.