If I want to monitor my work thru firewire to analog rca tv. what is the cheapest way?

Firewire output -> Analog RCA TV

I saw on a ebay a defective Sony TRV19, defective defective playbck and defective optics. it has a D/A passthrough selling for $150 worth it?

The TRV19 can't do analog --> DV, although it should be able to do the other way around.

The TRV22 can do analog --> DV, for turning analog material into DV.

2- Don't you already have DV camera?

If you only need to transcode analog <--> firewire (and not record to tape) then you may be better off with something like this:

http://www.bhphotovideo.com/bnh/controller/home?O=productlist&A=details&Q=&sku=389754&is=REG&addedTroughType=search

This box also has s-video and component video, so you have a much better quality connection to a good monitor than a cheap camera will offer (will probably be limited to composite video). It also does both PAL and NTSC if that's ever needed.