ProLight has an R8 spindle. F1 has a BT30 spindle. I don't know if it has the counterbore to accept NMTB30 tooling.
The ProLight had a 5000 or 10000 RPM spindle option on the stepper motor PLM1000 model. F1 tops at 2000 RPM.
The PLM1000 should have the same 100 pound working load of the servo motor PLM2000. Manuals for both are available to download from Intelitek.
I'd have to check for sure but it looks like the F1 has a smaller table. It only has two T slots VS the Prolight's three. (I used to have a 12 speed Drill/mill and the lack of a middle T slot was a big pain for setups.)
If you get a PLM1000 and want to use it as original, you must get the big black box AND the ISA or PCI interface card. Without either of those, you may as well take everything off the mill except the motors and get new electronics.
There is Windows control software for the PLM1000. Nobody at Light Machines or Intelitek bothered to make anything but DOS software for the PLM2000.
More info on the F1
http://203.159.5.16/faculty/bohez/data/EMCOF1CNC.pdf