So I messed up when I thought it would be a good idea to stick some hard drives into my NAS. It's now changed the partition table to a RAID0 one and my data has vanished. What are my best chances of recovering it?
With the slim details you have provided, your best bet would be to seek professional data recovery assistance.
Most reputable companies will ask you what you have, what you need recovered and give you an estimate on the costs for recovery without needing to charge you for their time to understand the scope of the problem.
Both are well familiar and capable at getting Mac formatted media and filesystems back as well as being fully professional in their skill at all other forms and format of data recovery. I've never regretted choosing either for recovery from personal up to enterprise needs.