apart from the bodies youll need an inlet manifold, throttle linkage, back plate, air filter, fuel pressure regulator, engine loom, ecu, engine map, a decent tight engine to put them on, ARP rod bolts at least.
you will be lost without a base map, its impossible to map yourself from scratch. this is a BIG advantage of sbd kits. SBD kit will also have a fitted, pre assembled engine loom.
tight is a bit vague really. but having been there and got many t-shirts, if theres any doubt about the state of the engine, maybe it uses a bit of oil over some months, maybe its racked up 100k and is sound in standard trim but could be better, do yourself a favour and spruce it up before asking more of the engine.
Does this mean its just a case of plug in and play? is it alot more cost wise if so is it worth having a bash myself.
yup. just plug it in. all the spurs are the right length, all shrink wrapped and labelled. they are VERY expensive though, like 350 quid expensive.
by far the cheapest method is rewiring a stock loom from your engine. i.e chopping off the standard ecu multiplug. working out which wire does what and goes where, then making up the pins for the new management with a pinout diagram.