isb gearbox replacement

[cnez]

Long story short, I want to buy a d series gearbox (sohc) open it up and replace the ISB and other possible bearings. Then put it into my car before the isb in my current gearbox fails. Before I go hunting what prices will I be looking at so I don't get ripped off?

Thx

[cnez]

Willing to attempt a diy before having to resort to paying the mechs labour for opening up my gearbox.