Great you don't go all emo on us. If I may suggest it, I'd start with some very basic practise on your bass (and get new strings and tune them ^_^). Your job as a bassplayer is essentially keeping the beat, so you need every note to be dead on. I practise this a lot. I've only played for a year now, and decided to start working with three fingers so I can keep up on the 500 and up BPM-parts of our songs, and what I do is start with a metronome (it is a little 'drum simulator'
http://www.metronomeonline.com/ ) at where I left it last time (say 150 bpm) and play quarter notes for 2 min then increase the metronome by 10 and try that speed. When I manage 10 bpm more, i put the metronome on say 50 and try hitting every note dead on the beats. It's extremely hard. Praticing slow and correct is extremely important.
As for you developing your skills, I suggest checking the forums for advice. There's so much good stuff on how to get solid on the basics! Then maybe take it past the basics, but then you really should start learning musical theory. I, for one, know little musical theory

It's certainly not a neccesity when playing songs and developing technique, but it enchance your understanding of what you play and makes it easier to make things fit with eachother.
Check out these threads mate;
Practice Practice Practice floating thumb techniqe Pacman's sure-fire scale practice method
As well as the other learning-oriented threads out here :3 So much good stuff, so many experience players willing to share with newbies like us.
And the place I learned basic muscial theory;
http://www.studybass.com/ . Such an awesome site.
Oh and if the guitarist is you friend, I'd suggest not ditching him

You can get better together you know, as long as you both are determined to become better players. Having a guitarist to practise with is awesome! Then again he might not be your friend, and you might very easily find a new one.