I guess it's not really paranoia. I don't even think OP is worried. It seems he/she's simply doing basic due diligence or research. He/she doesn't have proof of acquisition anymore since he/she's an early adopter. He/she could indeed encounter related problems along the way. You know exchanges these days.
Considering that many exchanges ask for proof of funds or proof of your source of fund or proof of wealth out of the blue, it's just indeed right to make some inquiries and solicit suggestions and recommendations from those who have the experience.
Yes, in that sense they are not very different from a bank, which requires proof of the (lawful) origin of your funds, or they won't even open the account and may report you.
The case of the OP has appeared many times in the forum, I remember at least a couple of threads in the legal section, where people who have been holding bitcoins for a long time, who have a lawful origin but cannot prove it, find that they now have a large amount of money, millions in fiat terms, of dollars, and suddenly appearing before exchanges, banks and tax authorities with such an amount will set off alarms and risk having them confiscated.
What I would do is, if you don't need a large amount, for example to buy a house, keep spending little by little well P2P, with gift cards or withdrawing cash in bitcoin ATM. If you need to withdraw all or a lot of money consult a specialized lawyer is a must.