i didn´t know that , but all f28 gearboxes here are to expensive and mostly trashed . and one off the bigest limitation in here is money.
here are some examples:
sold redtop c20xe with gearbox for 500 euros , bought C25XE with gearbox AC , front suspension , and brakes with discs (converted form 4x100 to 5x110 now it has 284mm discs ), half leather seats , alloy wheels,and lots of small parts for 800 euros.
the f28 gearbox costs about 3oo euros moustly one or two gears broken
and the service for that is 2oo euros. so for now its out of mine budget.
but allways something come along so i probably find something.