g77 and Lahey fortran 77

[MR]

HI GCC and G77 gurus, 

I am interested in knowing how hard it will likely be to get 
a fortran program written for dos in lahey fortran 77 to compile and
work under linux.

I have inherited a nice environmental model, that is badly in need of
updating, and restructuring.  I don't know much about fortran, but want
to incrementally convert it to c++.  It's a leisure time project, with 
good potential to be useful.

Anyway, any advice greatly welcomed.

THanks, 

Matt