Where to start?

So, I have had my Defender 110 truck cab for a couple of years and apart from replacing the rear brake lights and removal of fag packets, I have done nothing to it.
This was going to be a 'project' however the starting point for it is rather confused.

This is a 300Tdi that has had various bits done to it prior to my ownership - winch bumper, home-made tailgate (rusting very well), 2 new doors (also rusting very well).

I use the thing every day for work, as it's cheaper than renting a skip. I would like to improve the thing and go play in the mud - we are limited over here, but there are a few decent lanes.

Obviously seating is an issue - being over 3ft 6" tall, I can't get the seat back far enough - I had thought of doing a sort of doublecab roof conversion, but was put off by the cost of 2nd hand roofs - cheapest I have seen is £500!!

I would also like to try and improve:
1. Lighting - the 2 candles at the front are worse than useless.
2. Ride / suspension - It does bounce about rather a lot when empty!
3. Sound reduction - pointless fitting a radio at this stage..

So, where does one start? Drive train? Engine? Ride? Bling?

3 foot 6??? And we thought pikey was short, do you have to use a booster seat?

Lighting easy get some led lights from ebay I got some and now lights bright enough I prob don't need headlights on and they are cheap fix. Ride prob u need heavy duty springs and show as they prob getting weak from being loaded most of the time easy fix again jus don't get britpart rubbish . And sound buy cheap foam matting like excersise mat or camping type jus cheapie stuff and spray glue them down there been a few threads on all these and some pics to help all can be done cheaply

Ok, Suspension -
As the vehicle is loaded up quite often and having had a scout-about on the web, would a good initial combination be the Terrafirma Big-Bore +2 shocks and some HD Springs on the rear be a good start?