Since you are saying Cabriolet and under 3K, we can ignore the Cabrio (many
people confuse the two)  I will attempt a summary of the major changes, I'm
sure I'll miss some.

'80  First year, early style dash, points ignition,1.6

'81  Electronic ignition, different dash, 1.7

'82  slight change to top frame

'83  newer much improved style vent windows

'84  transition year!  1.8, close ratio tranny, 100 mm CVs, space saver
spare are all introduced

'85 name change to Cabriolet from Rabbit Convertible

'88  factory wide body kit, 4 round headlights

'90  Digifant II fuel injection

'92 last year of production

Some where around '83/'84 power steering became available and later models
had froo froo options like power windows and locks.  Final production had
air bags.  My recommendation?  Anything from late '84 up.  The 1.7 was
designed for the American market and is worse than the 1.6 it replaced.
Tops are very complicated and expensive to replace.  Later model trannies
are not as sturdy as earlier, but rebuilds aren't bad.

Scott

ps  this car was rated by Playboy for several years as the best car to buy
your wife/girlfriend!