I am not sure how to answer your questions, so I'll at least provide a few resources and see if this helps.
First, we have plans for farm structures which are free. The plans should give you ideas on usage of current buildings and what repairs may need to be made. Here are some resources:
We have Barn Again resources which review ideas for old structure, possible grants and reasons for repairing/updating. The website is at: http://fabe.osu.edu/extension-outreach/barnagain
Thanks for your question!