It can make a difference in your negs, albeit not a huge one if its off by that small a margin.
keeping the chems at temp is easy. any large (bigger the better) cheap slow cooker can keep your temps very close to 100 for the entire process. I got a cheap one at walmart for under $20 after thanksgiving that is perfect. just set the temp dial and you are all set. I use two thermometers to make sure the developers atay at 100. Do allow time for the chems to come up to temp and then stabilize as well.
Here is a great link to a site one of our fellow board members put up that helped me