Node Structure?

Structs are value types, not reference types. Node parent gives you a completely new value for parent, not a pointer to the parent node. You most likely want to use a class for self-referencing objects.

Performance is likely not a problem (although you may need to use object pooling at some point to avoid garbage collection issues). And you should only worry about performance after you've used the profiler to identify areas of the code that are causing performance issues.