Path to PERL:
/usr/bin/perl or /usr/local/bin/perl
For more common values needed in CGIs, please refer to this useful article in DreamHost's Knowledge Base:
Where to install MT:
according to Robert's instructions, install MT in a sub-directory within your web directory.
If you are still experiencing problems and cannot get anyone else to help you, please feel free to send me a private message. I am happy to give it a go at installing MT for you--for free.
Disclaimer: I am no MT guru (read: I offer no guarantee for my work!), even though I did manage to install the software on my DH account successfully last year.
All the best,