Yes, you as the LL are liable for the cost.. check your LL insurance policy to see what's exactly covered plus weigh up your claims excess payable if any.
Get a couple quotes to repair and to replace the entire oven (it may be cheaper).... dont forget the repair is tax deductible and a new oven deppreciable.
I get my PM's to organise all the quotes, repairs, replacements, lodge LL insurance claims etc etc...thats part of what I employ them to do.
I hope this helps.