Growling may be a warning to leave the dog alone or it will escalate to a bite, or it may just be complaining. My first Basenji would snarl and scream if I picked her up when she was comfortable, but I just laughed at her and she never followed through on the threat. My second girl would "swear" if told to do something she didn't want to do, and would snark if you moved her when she was comfortable, but again there was never escalation. One out of the five Basenjis I have owned would follow up the growl and bite if he was upset, but generally I have found that it is usually just their way of registering displeasure. Resource guarding can be tricky to deal with, however, and may result in biting if the dog is serious about retaining "his" possession. This gets dangerous if he gets hold of something that could be harmful, so personally I don't like to let it go. My own feeling is that if the dog has something that is indeed "his" that has been given to him, e.g. his dinner, then I won't provoke any confrontation, but if he has stolen something then I will take it from him immediately, no playing games, no "trading". The last thing I want my dog to learn is that stealing items is a good way to get rewarded with treats!
Regarding personal space, I have generally tried to finesse this rather than confront it. Many Basenjis will snark if disturbed when they are comfortable, and in my experience this does not change with time. If I need the dog to move, I may issue a command, but what has generally worked for me is to sit down next to the dog and gradually, with honeyed words and patting, maneuver said dog out of the comfy spot. I can usually avoid direct confrontation and manage with barely a grumble.