Tooling required depends what is wrong with it. Needs a proper diagnosis first. If the oil damper needs a rebuild then it's a castletool, bullet tool and shaft clamps.
The trouble is that you need to know what you are doing to know you need the later two of those tools.
If these forks go anywhere near any wrench who doesn't know what they are really doing then they will be returned to you in a bin bag.
If you really want it done properly your options are take it to a Cannondale specialist in the UK - there are a few - or post it to Craig Mendon in the US.
The later is more likely to work out TBH.