I wouldn't go with the slip collar. It sounds like your pup needs work on pulling and on-leash interaction. Honor has recently taken to barking and lunging at other dogs, so we're in the middle of this work in progress as well.
For the pulling: Everyone has given you great advice in "make like a tree" when your pup starts pulling. This method really teaches the dog that pulling does not get them closer to the object/smell/sight that they desire. This method can be long and pain-staking, but well worth it. Even if it takes 10 minutes for you to reach the end of your driveway, be consistent and don't let up on the training. To make things less stressful, I would definitely look into the Easy Walk harness (by Premier). Every dog is different, but I've had GREAT results with Honor with the Easy Walk.
For the lunging: You'll first need to identify what your pup is lunging at (ie. bikes, kids, dogs, etc). Then you need to begin the desensitization process that Leslie mentioned. There's a couple ways to go about this, but the main idea is that you gradually introduce the stimulus to the dog at decreasing distances. For instance, say that your pup lunges at dogs (Honor's problem). We've been working on gradually approaching other dogs, first starting at a distance where the dog isn't reacting. It's especially helpful if you have a friend or family member with a dog who isn't leash reactive, so they can assist you. Say that your pup's comfortable distance is 50 ft. You're going to want to praise and treat for quietness and attentiveness. Gradually walk toward another dog. The second that you see your dog tensing up (or showing other signs), make a turn away from the dog, and praise for quiet attention again. It takes a while, but you'll gradually cut this distance down until your dog is comfortable meeting another dog on-leash. The point behind this exercise is that the dog eventually learns that approaching the stimulus quietly means praise, treats, good things, etc.
Another method that has REALLY helped Honor is what I term the "hide behind the fixture" technique. This is especially helpful when you're having problems in a training class. To illustrate it, I'll just explain what I'm doing with Honor, if that's okay. When Honor starts barking repeatedly and pulling toward another dog in class, I'll first try to regain her attention, but if that doesn't work, we leave the ring and go into an adjoining bathroom or hallway. By removing the stimulus, she can regain focus, but she's also picked up on the fact that if she goes barking-nuts, all of the fun stops. Honor's problem is that she DESPERATELY wants to greet every single dog she meets, but she's having a hard time accepting that she can't do that all the time. When she gets reactive, we leave the situation. After she calms down enough to perform simple commands, we'll re-enter the training ring, and I click and treat for quiet and calm behavior.
You can also use this pretty effectively if you have a Petsmart or Petco with a training class in your area. When Honor was first learning that dogs=calm, we would work on approaching the training ring of other dogs, gradually desensitizing with the added bonus of having other aisles handy to utilize if she got too crazy.
I too would recommend looking for a good positive-reinforcement training group. A good trainer will willingly discuss your training issues and goals with you, and I think that your pup would benefit from the socialization aspect of a group class. And as for teaching an automatic sit when you stop, I wouldn't worry about that until you've got the pulling thing resolved a little bit. It's a very good behavior to teach eventually, but I might break things up into baby steps for now.
Sorry about the novel-length of this, but I'm in the middle of this sort of thing now, so it's fresh in my mind. Good luck, and feel free to PM me if you want to talk more.