The porting is only to allow more airflow to the intercooler.
There is plenty space to sandwich everything in.
Radiator: Engine Oil Cooler: PAS Oil Cooler: Intercooler: Fans.
You should be able to squeeze everything in with the oem crash bar fitted.
I ran for a while without one but decided I wanted a bit more front end protection.
Should just pop off once all the bolts are removed, however may require very, very, gentle persuasion to break the seal.
My guess is that you have missed a bolt.
Get all from the Traders on here or gaskets and seals direct from Nissan and the bearings from here: http://simplybearings.co.uk/shop/index.php?cPath=4747_4514&gclid=CO-t_77r7coCFTAz0wodVqUHwg
This is the way to go as you have to many questions.
There are a few in your area, however if you are ever up in Perth, then swing by and I will take you out in the 666bhp 350. which has a twin plate ATS Carbonetic fitted.