I just did this same project myself on Sunday and used the instructions provided in the following link:
https://sites.google.com/site/mikefocke2/BOXSTERConvtopconversionPARTIformatt.pdf?attredire cts=0
- Scroll down to page 11 of the PDF file and start from the bullet point called: MECHANICAL PART OF REMOVAL/INSTALLATION OF TOP AND FRAME ASSEMBLY
I found the guide to be very helpful and easy to use. Good luck!