bcfc.
Did the same myself, PPL on C150's & C152's and now converted to PA28.
I found it quite easy to convert and it took a couple of hours of general handling and circuits with an instructor before he felt it was OK for me to 'solo'.
The PA28 is a nice aircraft and is easy to handle the only quirky thing for me was having manually operated flaps instead of electrically operated flaps (at first I thought the flap lever was the handbrake
).
I would suggest that you get a copy of the PA28 pilot notes published by AFE or the aircraft manual to read before you convert as it contains all the technical info you require but no doubt your instructor will brief you before hand on Vspeeds etc.
I didn't find the 'high wing low wing' thing too much of a problem, its true that your view of whats beneath you is obstructed but then you can see better in the turns especially in the circuit. Its just a case of adapting.
Happy Flying
PK
[This message has been edited by Puffin Killer (edited 01 May 2001).]