Holy crap that had to be scary. Did you just buy this car?.. your lug nuts could have been loose... I would check the rest of the tires before you do anymore driving.
For the swap.. you are generally looking at about $1,800 - $2,500 for the clip. Make sure what you get is complete though.... can turn into a hastle.... know from experience. I got lucky and got all of my missing parts from a member on this board.... but missing parts are hard and pricy to find. If you can find a half cut you would probably be better off. People generally say that selling your N/A and buying a turbo is cheaper... which basically was true in my case. I think if you get a good complete clip, and do all labor yourself... it shouldn't cost you more than $3k.. that is at the MOST. Driving the turbo is nice

. I highly recommend the swap.
There are many shops around that 'say' they have 3S-GTE clips... but most of them don't. The only place online that I found that had them in stock was
http://www.flashoptions.com . But I don't know how reliable they are. I got mine from
ARD Performance, but I live in California so I just drove down to San Diego and picked it up. They do ship though.... not sure how the pricing is but they do it. I did all my buisness through a guy named Dennis, he is the manager. It was missing a few parts (intercooler, downpipe, coils/ignitor, air flow meter, 1 missing axle), but this thing is extremely clean... I was very surprised. I paid about $2k for it.