Doing Pull ups

This is a question for anyone that has any advice on how to do a successful pull up. I NEED to be able to do pull ups as it's one of the things that my coach includes in our training. I've been training all year on building my strength and I am so close I can just taste it. My coach told me the best way to learn how to do a pull up is to do negatives or the lat pull down machine or the assisted chin up machine, ranked from best to worse way to learn. I've been pretty good at increasing my strength and can now lift 115 lbs so I am pretty darn close to my goal. My problem is that I've gained weight (around 5 lbs) bringing me to about 130 lbs at present. Now, I know it's not all fat that I've gained and that it's most likely muscle because 1) I'm stronger and can lift more and 2) my clothes fit better :-). I know that I have to step up my endurance level as I've always found I needed to do that (started running last year and I've improved quite a bit but still need lots to improve). I hate cardio but I do it out of necessity. Right now, for cardio I use the treadmill and do interval training on it for half an hour. Not quite sure if I can step it up to more than half an hour of interval training as it just burns right now. What I've done for my cardio is keep it at around half an hour but up the intensity. During my dry land training I will be doing interval training and some long pieces on the treadmill too.

So my question is, what do I need to do to actually get to that point where I can do a pull up? Should I increase my cardio and try and lose/maintain the weight I've gained? If I do that, would I be losing muscle mass and therefore decrease the amount of weight I can lift? Or, should I keep increasing my weight so I will be able to lift more. If I do that, I'll gain weight which isn't THAT bad since it will be muscle and not fat. But then I'll have more to lift.

My season has just ended and I will soon be going into some dry land training. I'll be designing my own work out so it would be great if people could give me some suggestions on exercises. My gym is pretty limited on some of the equipment available. However, that being said, I do prefer exercises that uses free weights and compound movements. So the machines that I do use are the lat pull down, seated row, and the tricep machines. Other exercises I incorporate into my work out are deadlifts, weighted front squats, clean and jerk (I think. I'm never sure what the difference is between this and a deadlift with pushpress), external rotation, dips with feet raised on bench, crunches, ruts, push ups, woodchops, kill the bird, and a many more exercises. Oh, and I also use the Ab chair too. I do like variety so I mix it up regularly. Usually, every 4 to 6 weeks. I am usually in the gym 2 to 3 times a week for 2 hours each session (weights and cardio). However, now that my season has ended I plan on going more often (hopefully 4 to 5 times a week).