the replacement cost is near $200. and as for starting simple and going from there? That's probably the approach I'll take. done allot of tinkering with different components as when my Dad passed away I inherited his "lab" and he was a pack rat! I think I gave away more computers power supplies and automotive electronics stuff than most people will ever buy in there lifetime...lol. I did keep his junk box and parts rack though, so I bet I have what I need rite out in the garage, but I digress. K.I.S.S. works for me. I'm familiar with how comparators work and I can sort of see your avenue of approach there and now that I think about it, I do have some big transistors out there too but I never tried to use them because I couldn't find any specs on them. That; I imagine would be the expensive part. but even spending some money on parts I'm pretty sure I'll come out ahead.Something Like a current sensor could be as simple as a single resistor, add a comparator chip (very very cheap) and you have an adjustable current limit. So many ways to do it.
Best plan is work out exactly what you want it to do, build a simple version frst, something very basic and take it from there, two years from now you will have a home lab
I appreciate everyone's help so far, and once you guys stoke my brains enough I'll even get brave and post a schematic for the group to critique . I love a challenge.