Hi,
A bit strange that only the latest Pk3 can program that device, yet its over 12 years old ?
You can program it with the Pk2 using the PK2 V2.61 application form the Pk2 site, though there is a v2.61 note saying it must have a full 5v VDD, so an external true +5v may have to be used when programming with a Pk2
However there is no indication that the chip has a built in debugger or if a external add on debugger would work.
Probably your best bet would be to port the code onto a similar 28 pin chip like the 16F872/873 or 876A chips all of which can run debugger direct.