Head unit wiring won't fit :(

[Stevo-M]

My better half got me a single din dvd head unit for christmas, but when i tried to fit it today i had a real problem getting it pushed in properly, due to the amount of wires, plugs and a big black box at the back of it. Does anyone have any tips on how to get it all tucked in? I have a B5 with climatronic
Thanks in advance