Are you valuing the land at €300K, because you want to impress bank for mortgage? What is market value? Could you have it valued (professionally) at less than €280K? At current rates, you would be paying slightly under €7K CAT. You cannot inherit from the living, you can only be given a gift. You inherit from the dead.
There will probably be stamp duty payable. Is there a farm involved? You might get certain reliefs if you are a 'trained' farmer and are going to use the farm as a farm.
As regards the transfer of the land, you should get advice from a tax advisor as to the most tax efficient way to have it transferred to you.
Why would you put your mother on the mortgage? Do you need her income to be taken into account? How old is she? Banks tend not to give mortgages longer than borrowers 65th birthday. Would your mother agree as if you defaulted, she would be in the firing line and she would certainly need to get separate legal advice before she could sign any papers.
Do you need to get mother to act as guarantor? Again, she would need independent legal advice.