Wanna help with my cover letter?

Sounds kinda lame doesn't it? I've never actually done a cover letter on a resume. I haven't a clue how to begin.
My resume has always been solid and straightforward. I fix things, hire me!

The problem happened in 2000, drinking too much, smoking too much, and not realizing I had high blood pressure. Something had to give, and it did, bigtime! I had an aneurism in my aortic arch, it blew while I was on the operating table. The doc said it looked like a grenade went off in my chest.
It's been a long recovery and I'm still not 100%, probably never will be.
My girlfriend took it upon herself to help as much as possible. She financed our 2 business ventures that helped me get through 5 years of not being able to do what I was used to doing. Three weeks ago we closed the doors on our store. Just wasn't making enough to pay the bills anymore. Now I have to get a real job.
I have this solid work history, a 2 year gap, then 5 years of being self employed. How do I put this into a resume and a cover letter without sounding like I'm a complete basket case? An employer needs someone to call to verify that you can do what you say, but my last "real" job was 7 years ago. How do I convince someone without telling tall tales that I really can do the job they want done?
I would like to be honest without telling too much and at the same time to sound agressive enough that someone would like to hire me.
I can fix damn near any machine, program a logic controller, wire up 440 volt lines,,,,,,etc. But I feel like the only place that's gonna hire me is wal-mart. "Hello, welcome to Wal-mart. Do ya need a buggy?"

Any ideas or suggestions?