adding equipment is easy, just 3 files needed and a paragraph for two of them.

for a new thruster you need these files:

st_good.ini
st_equip.ini
market_misc.ini

now st_good.ini

[Good
nickname = ge_s_thruster_05
equipment = ge_s_thruster_05
category = equipment
price = 8000
item_icon = equipment\models\commodities\nn_icons\EQUIPICON_thruster.3db
combinable = false
ids_name = 263740
ids_info = 264740
shop_archetype = equipment\models\st\ku_thruster.3db
material_library = equipment\models\ku_equip.mat

next st_equip.ini

[Thruster
nickname = ge_s_thruster_05
ids_name = 263740
ids_info = 264740
DA_archetype = equipment\models\st\ku_thruster.3db
material_library = equipment\models\ku_equip.mat
HP_child = HpConnect
hit_pts = 8000
explosion_resistance = 0.500000
debris_type = debris_normal
parent_impulse = 20
child_impulse = 80
volume = 0.000000
mass = 10
max_force = 72000
particles = gf_ge_s_thruster_01
hp_particles = hpthrust
power_usage = 100
lootable = true
separation_explosion = sever_debris
LODranges = 0, 20

next market_misc.ini to sell it at manhatten we goto Li01_01_base and add this to it

MarketGood = ge_s_thruster_05, 0, -1, 10, 10, 0, 1

and you have a new thruster sold at Manhaten, of cource though you need to change the ids_name and ids_info.

If you check the thread that says it has it all, then you will find links to pages where it tells you how to make new engines, power plants, shields, weapons, thrusters, etc etc