Tableau is still a 32bit application, your OS will be 64bit so the maximum amount of RAM Tableau could use is 4Gbytes. BUT, in near future they will release a 64bit version, (don't ask me when exactly) as a result a safe bet will be a minimum of 8Gbytes RAM.
Ask the vendor if the hardware support an upgrade to 12 or 16Gbytes just to be sure where the wall is situated.
I see that you are struggling with .tsv files, i will recommend you to check the following tools:
- data wrangler http://vis.stanford.edu/wrangler/
- google refine http://code.google.com/p/google-refine/
- csvkit http://csvkit.readthedocs.org/en/latest/
- ms data explorer http://office.microsoft.com/en-us/excel-help/start-page-HA104003813.aspx