Yes, it can be done. Kodak did it to create the 14n and Fujifilm did it to create the S2. It probably cost them millions of dollars in R&D to do it, and the resulting cameras cost in the thousands.
If you want to do it yourself, it's not going to be easy or cheap. Unless you can make the chips yourself, you'd have to cannibalize another digital camera. Then you'd have to design the internal layout, position the parts properly, and so forth.
It would be a lot cheaper and easier to just buy a new D3200 or D5200, or a used D80 or D90.
Answers & Comments
Yes, it can be done. Kodak did it to create the 14n and Fujifilm did it to create the S2. It probably cost them millions of dollars in R&D to do it, and the resulting cameras cost in the thousands.
If you want to do it yourself, it's not going to be easy or cheap. Unless you can make the chips yourself, you'd have to cannibalize another digital camera. Then you'd have to design the internal layout, position the parts properly, and so forth.
It would be a lot cheaper and easier to just buy a new D3200 or D5200, or a used D80 or D90.
No, nothing practical for an individual. Kodak and Fuji both adapted the N80 chassis to digital -- Kodak's DCS Pro 14n and Fuji's S2 Pro.