I know enough about manifoils to know that you will have a very hard time opening it. Many regular users still struggle with the dialing sequence and they have very little tolerance. You will need to be directly over the operating mark to align it correctly.
There is a reason that manifoils were fitted to government containers here in Australia (still are in some cases). It is challenging lock for experienced locksmiths and safe techs, so it's going to be quite a stretch for a novice.
There is no "easy" way with a manifoil. You either find someone who can manipulate one (rare), knows his to set up their dialler for one (not rare, but there will only be one or two in Melbourne) or you get someone who can drill and repair with minimal damage (there are ways, but that is not a conversation to be had here).
Is the lock actually already open? Old safes can be unlocked but seized. Either by virtue of corrosion or grease hardening on the bolt work.
If you want a DIY project you are going to have to learn a lot of fundamentals before you are ready to tackle this project with any semblance of professionalism.
You may want to consider posting in the public enquiry area of an Australian professional locksmith forum (try Locksmith Trader Forum) if you are serious about engaging a professional within Australia or getting some background on your lock and safe.
Listen to oldlock, he actually knows what he is talking about.