1 Is it a good idea to export a VM from one server and import the VM into a completely different server?
2 Would there be any issues?
3 or is it better to just reinstall and reconfiguration everything on the new server (this is good but its rather time consuming).
Sure. I have done it a couple of times with no issue. I would recommend using XenConvert 2.1 to move the VM to the new server. It will take care of creating the destination VM and migrating the OS. You can even resize the partitions.