Sometimes they send them back to Viking for some repairs. I know my Mom's ruby ... they only do simple cleaning any thing else goes back to Viking. Is your machine even at the shop? If you have opportunity check to see if its even there. If it did indeed go back to Viking ... they ( where you dropped it for service) need to be more aggresive in finding out the status.
All that being said ... it really should not be taking this long , no matter who has it.
Do take the loaner.. I know its not like your very own machine , but why suffer , It may even help them get a bit more urgency in getting the reapairs done , knowing you have one of their very expensive machines.