A telescopic downdraft vent can be installed behind most cook tops. Here is the installation manual for a common type of telescopic downdraft vent (Kenmore model 59966):
Use & Care/Installation Manual
. This should give you an idea of what you are looking at regarding this type of vent. You may be able to use the same vent for this unit that you used for your downdraft slide-in range.
Even though this telescoping downdraft vent can be installed behind most cook tops, you would not be able to install an oven underneath the cook top. You would need to install a wall oven in another location. Keep this in mind as you make your decisions.
Replacing the slide-in downdraft range with any other configuration of cooking appliances will require significant counter construction. I recommend that you consult with a local contractor regarding a major revision. If that revision will cost too much, I recommend that you consider replacing the downdraft slide-in range with another current model of downdraft slide-in range. Jenn-Air still manufactures several models of downdraft slide-in ranges. Here is a Sears.com link for one model:
Jenn-Air Stainless Steel 30" Slide-In Electric Downdraft Range w/ Convection JES9800CA
Replacing a slide-in range with a cook top and a conventional range hood will also involve significant cabinet work. You will also need to arrange the venting to the outside of your home unless you want to recirculate the exhaust air back into the kitchen after it passes through a grease filter inside the range hood.
If hope that this information helps. If you need more assistance, reply with additional details.
If you need a contractor to help you with this remodel, I recommend that you consider the pre-screened professionals on the ServiceLive.com website. Here is a link for that website: