If the basement was finished legally, that is, with permits and inspections (even if it was used as an illegal unit later), you should be able to do what you propose without having to offer your first-born in return.

Things to check out:Were permits pulled and paid for?

I think the new appraiser is low, but there turned out to be permit issues and I think that had an effect.

.- Find an agent who will "share" access with you (though this is illegal)Where Jason used the term "illegal" in that post above, I think a better choice of terms would be: "not permitted under the rules of the MLS, and could result in the agent losing their access to the MLS".

Get busy with permitting (things like getting permission for the driveway cut-in from the road, perk tests, maybe septic design.)

You are not dealing with demo, plans, architects, permits, surveys, constructions, loans, etc.

In the meantime she wasn't pulling the permits she said she was pulling and when she did finally pull them, she pulled them fraudulently under a different contractor's license.  

Did you have to pay for permits?

I hear Garland/Mesquite inspectors can be pretty strict so budget more for permits etcAnother example may be the local rentals/ rehab market requires updating to double-pane windows.

Your market will determine whether the extra bed/bath ( my guess) or the garage is more desirable, but get it permitted if you convert.