what special tools do i actually need ??
Depends upon how much you can fabricate yourself. The list is quite formidable with many fixtures being single purpose, and includes RMS and IMS tooling, cam timing equipment, special tools to hold the rods while putting the cases together, etc. You can easily spend more than a few quid getting ready to do one of these engines.............. If you can find one of the early printed OEM manual sets, they list the required tooling and fixtures.
Google Laser Tools 4717. I'd say that was the bare minimum you will need. You can buy them for about £400 if you shop around. I bought a set for a friend direct from the manufacturer in Taiwan, and if you drop me a PM I'll pass on the contact details if you want them.
Same tool set is available on eBay for $399 US. Just look for Porsche 996 tools.