I think my tranny is done, so I need a 5 speed kit

[laserx]

I was just leaving my office and I felt like something slipped in the frontend for a second, then grabbed and off I went. In 30 seconds or so, suddenly my car has this continuing loud clunking sound that seems to come from the front of my tranny or diff. I had to get it back to my office to park it and rent a car. I looked at my dash and saw that my speedometer was no longer working, it sat at 0 even though I was moving. I manually shifted to 3rd, and the car did down shift. I clunked back to the office. The check engine light came on (speed senor I imagine).
This is my 3rd transmission, if this is the tranny I want to have it converted to a 5 speed, where can I get a kit and instructions?
My son is a mechanic, he said he'll do it if they'll let him take it to the shop, so labor is not issue. I plan on buying another car for the winter tomorrow so he'll have all winter to get it done. So can someone recommend a place to buy a conversion kit, thanks.