There are books on the GR5 with the times and all the info. Try any mountain shop like Cactus or one of the big Naville stores.  If they do not have it they will tell you where to get it. 

iun fact this is probably the best.  Do not know the book but have bought other Cicerone books before and find them good.  In English and give a day by day description.  I think you will find in the shops I mentioned -é otherwise on line

http://www.cicerone.co.uk/product/detail.cfm/book/533/title/The-GR5-Trail

The best thing if you are not sure is to do the first days walk and check your time against the book. 

I have done some sections of the trail and found them easy but am not sure about chains.

I did once meet a German couple who did it with a dog but it was a special dog and I met them them at the top of Mont Blanc - with the dog!!

The thing to bear in mind is that the trail goes through National parks where in France you are not allowed to do it even with the dog on a leash. Of course French people ignore this but it should be respected.

If I were planning it myself I would dispense with the tent and take a light sleeping bag.Karrimat mattress and planty of light underclothes eg jambiere wich are synthetic tighs but with no feet worn by cyclists in cold weather, gloves and hat.  Then if rain is forecast I would get into a hut or cheap hotel. 

Re food the book will explain where the path goes through villages, so would be surprised if you have to take more than 2-3 days of supplies.

Should be great Just do not hahve the time to devaote to doing it one day.

Have just downloaded the sample route from the website - seems idiot proof but would recommend talking maps,. Up to Chamonix you can download the maps for free (put Swiss Federal Maps into your search engine - thank translator for this)) 

A friend of ours has done this exact trip: she was sometimes on her own, sometimes with friends, and sometimes with people she met en route. It took her 6 weeks, staying in overnight accommodation [hostels] en route. She is a very experienced walker/hiker and I would put you in touch with her, but sadly she has moved back to the United States.

Two years later, she walked/hiked from Luxembourg back to Lac Leman, an equally exciting and entertaining experience for her. Good luck and bon voyage

The book I referred to above suggest 1 month for the walk but I would think 1.5 months more resonable - rest days etc.  * months seems far too long unless one month is spent on the beach at Menton

thanks paul - very helpful !!