The first thing, as with ANY repair / restoration / restification is to start by documenting the condition and details of the subject. Photos, photos, photos... and more photos. At every step!
Locate as much information,technical, sales and promotional, etc as you can. Search for and any available join type clubs.
And finally, start disassembling, tagging and bagging all part and hardware.
Does the RF4(?) have it's original covering, or has it been recovered in the past (45 yrs)? What condition is the covering in? Has it been hangared or stored outside. Use a punch tester to evaluate it. How many (if any) inspection ports are on the lower surface of the wing? They are easily installed. Video inspection cameras are quite common now and inexpensive. At this point, you should be able to make an educated decision whether to retain the existing fabric, or to strip the wing completely.
If repairs are needed, then you will almost certainly need to strip the fabric. If funds aren't an issue, then I would default to replacing the fabric. Will certainly make inspection and repairs easier.
Inspect general condition of all wood for cracks and breaks, glue joints, corrosion, cracking and security of all fittings and hardware, delamination of any plywood, etc...
Personally, I think the Fournier is an incredible aircraft. Are you familiar with Mark Calder? He designed the Wren ultralight in the late '70's, and has for the past few years developing an FAR 103 RF4 replica called the Robin.
Hope this is helpful. Looking forward to seeing your progress.
Mike(y) in OR