Completely installing the JLF isn't necessary. All the measurements are the same, so the micro-switches are what makes the difference. With the JLF switches and the octagon plate, you won't know the difference.
1.) If you have a JLF stick then remove the mobo that is holding the switches and then get some cutters and remove the switches from the mobo.
2.) Unsolder the old switches and place the new ones from the JLF in. They should fit with no problems.
3.) Then re-solder the original wires to the new switches and your done.
The all the shaft components including the shaft can stay. Side by side, there is no difference between a stock Sanwa and the modded one that I just explained. Though I do recommend the octagon plate.
The most tedious part is the filing of the button holes. The rest of it I found relatively easy. Besides, you feel much more proud when you complete this that just swapping out some buttons in the HRAP.
To MarkMan, have you ever thought of just building a Saturn usb controller? I found a site with a tutorial and it doesn't seem too difficult.