This is a good question no matter what anyone says. And even if you're inexperienced you can have a dog! You can easily study up!
So don't listen to those other people... Anyway I grew up with Rottweilers. I have a beautiful 8yr old female and she is very docile except around other dogs, but that's because we didn't have her around many dogs growing up. Rottweilers are just as well-natured as the next dog.
They have a bad rep because they're big and scary so people tend to use them in dog fights or for guard dogs. I had another rott a few years back who was playful as can be and didn't even mind the company of cats and honest to god we didn't spend one second training her (she just did what she wanted regardless). You should judge this situation based on how your lab reacts with other animals (like how does he react to dogs when you take him on walks or to a park or when he's inside and a dog walks past the house).
I honestly think you should stick with the dog you already have. Rottweilers are not for the inexperienced, which by your own admittance, you are. In most cases, with good training, dogs can live in multiple dog households.
If you want another dog, and your circumstances will allow, why on earth not get another of the breed you already have (given that any female you might get MUST be spayed before her first season, unless you go get your male Lab. Castrated before you buy a female (pity to do that because spaying her will sort all that out!). At least by now you'll know a thing or two about owning a dog.
Ps I'm not sure what age 3 'in dog years is', but is he still a puppy? If so, get him through his puppyhood BEFORE bringing in a second dog.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.