A question about 29er tyres and 69er's.

Since my crash in the summer i have spent all my time on the road, either commuting or mostly doing short hour long fitness runs and the odd half day'er. I switched to rigid forks, narrow flat bars and slicks and so the bike looks more like a hybrid than an MTB these days.

My intention is to go 69 for the summer; keep the rigid carbon forks, pop the bigger wheel on the front and do some light trails, paths etc.

My plan was to keep the slicks for now as the 26'er and then go lk knobbly offroad 69'er.

I have a couple of questions though.

Firstly, is it possible to go full slick as a 69 set up and if so would my road ride be awful? Would i notice much of a difference from running my standard 26 set up, moving up to a 29 up front? Im currently running Conti sport contacts.

Secondly i cant seem to find a 29" slick. Would i need to buy a 700c instead? Of course if the thought of going slick 69 wouldnt work then id just get knobblies and stick to 26 for the road.

Any advice would be appreciated.

Thanks
Matthew