OK you can source and render to the same hard drive as long as it is big and fast, I would say that despite what others might say if you are working with 60fps HD files even if the project totals only 50 gigs, you need a working space drive for the files of at least a 256gig SSD.
Make sure you grab any updates for Vegas, seems trivial but important.
Also many programs will automatically store thier temporary working files on the same drive as the program install, so go through the preferences tab and make sure that all the saves and all the temp files are being routed to a drive with shitloads of space. If you have 3gigs left on your SSD and are getting a render fail it may be failing when the SSD is full of the partially rendered temp file before it even makes it to your work drive.
Ok 5 rows should be fine, my current project is 9 sources (each in a row), of 1080i HD video and 24/96 audio. I have heard of projects with a bunch of rows doing wonky stuff.
rendering each line wont help, and lowers your output quality potentially
Good test for first project and new build:
You want to lower the amount of resources you need, shorten your project be splitting it into smaller pieces f the timeline so - click on a spot in your time line maybe 1/4 of the way in or at a scene edit perhaps, then edit>select>all>edit>split>save as now call the new project thebigprojectpt1 or whatever works for you and then delete everything after the split. Now keep your original project file with no work done other thatn aligning the clips as well. Do your rendering on the new "pt1" file and see if you get a new rendered file or another fail.
What are you going to do with your final file?
DVD, blu-Ray, youtube?
123 mins sounds like a concert (my projects are as well), and if you set up things right in project settings and by making the right choices in rendering, the computer can do less processing. Since your source files are different types, you can allow Vegas to adjust the files to the project specs as you import them (not add them to the timeline). This makes each import take longer, but reduces the back end processing time alot, of course you would have to start the whole project over and fix your settings at the start.
Also just a guess but if you added the 60fps file first and make that the default setting for the project or render to any 60fps format you are going to bloat all your sources to that format and make the size bigger than the quality merits, so unless the 60fps footage is super badass ninja dope, I suggest making all your settings match either your 1080 or 720 youtube footage.
hope some of this helps, doing a full length 1080 multicam concert vid is a mother the first time
additional questions, etc gladly accepted, I have learned a bunch of stuff on this forum and am happy to share my own meager knowledge
Dave
Don't get discouraged, I just checked and my first project took me more than a year with only 2 video sources and 1 audio source
http://youtu.be/4sXIzGboHYk