Again, to echo Ron and John, welcome to the board and to the Cub Family. I am sure that you are going to be very happy with your 48. I have a 48 and a 51 - the 48 is Elie-Mae and she runs like a top (after some serious TLC) and Jethro is the 51 who is in dire need of a rebuild
First take your generator to a good shop and have them bench test it and repair it if need be. You will be glad you did.
Second, install your generator. There is no need to convert to 12 volts as must be done if you install an alternator. There are many views on this, but I look at it this way, it was designed as a 6 volt system - positive ground, has worked for nigh on to 60 years, don't monkey with it
Ellie is still a 6 Volt system and she works beautifully.
Third, visit the Manual Server
and read up on the stuff available on the server and through the links, especially the Cub Info, Cub FAQ's, the Best of H.L. Chauvin and then the Owner's Manual.
Fourth, as John has already said, go to Binder Books
and get these three manuals:
TC-37F Parts Manual
GSS-1411 Service Manual
These were the first things I bought when I bought my tractors and they have been invaluable.
Also, check out the Blue Ribbon Service Manuals - the Generator is extremely well covered and should help you put it back together. Also, the whole electrical system is covered and is a very good guide for putting it all back together as well.
Fifth - and this is the important one - ENJOY YOUR CUB!!!! She will give you tons of fun and enjoyment over the years.
Again welcome to the world of Cubs