Moving oven and cook top - help please
You will need 2 new 240 volt circuits, The amperage requirements will depend on the specs of the units you select. Running through the attic is probably the best option, other than tearing out wall covering (which you may have to some of regardless).
As to reusing the old oven wiring: probably not, these units were often run with SE cable (2 conductors and a bare ground. Not acceptable by todays code. You need 3 conductors plus a bare ground for all appliances rated as 120/240 volts.
Costs will depend on the locality, the type or cabling required and the difficulty in installing the new cabling. Coud be as little as $500 but could be well in excess of $1000
Coastal South Carolina