I'm a bit relaxed about the whole 'ex' thing. That said, I wouldn't want a 'warts and all' biography and comparisons are a definite Noooo!! I know very little about my partners ex and yet, bizarre though it may seem, we sometimes go and visit his mum and dad. They were very good to my partner when she was ill, often ask her round for dinner etc and she wants to keep in touch with them. I don't have a problem with that, and neither do they. I wasn't the cause of their relationship breaking down, it just fell flat and they parted by mutual consent. He's moved on, my partner has moved on and there isn't any point in getting huffy about mentioning his name. It's a bit ludicrous to imagine that anyone over the age of 18 hasn't been out on a date with someone else (at the very least!) and doesn't have any history, just keep it away from the bedroom stuff and offering up examples of what they did that your partner does differently and if you are both adult about it, it should be fine.
Presario, that must be so awkward for you :-( Your guy must be really insecure. If he isn't mature enough to understand that you were with one person for all that time and you have history are you sure he's the right person to be with? Why should you have to lie to reassure him and ease his paranoia?