Pt Crusier pc ( computer board)

Bought a 2005 Pt Crusier two months ago.  
The check engine light came on had it
scanned and 3 transmission codes came up
was told by the garage to take it to Dodge
They  say we need to replace the PC as it’s
not communicating for $1800 they also say
that doesn’t guarantee the transmission isn’t
having problems  this spedometer stopped
working iand the vehicle is surging  my
question is should we throw the $1800 to fix
it or we just throwing bad money after bad
money it’s a first car and we paid $3000 for it
what’s the chance the tranny will pstill need
replacing what do you think it’s just because
computer isn’t working ?