Well, doing any of this would probably kill your resale. And as to the financial cost, I can't really see it making sense.
My 1998 C230 is worth about $30K retail. A new C240 would run me about $42K. I can see the transformation kit adding up to at least $5-6K. Now I have a $36K 1998 C230 that's probably worth $25K. This body update set me back $11K. Take the money, and buy a new C240.
1998 C230 "Black Betty"