Made a visit to a local computer repair shop

Sounds pretty cool user. I think you should continue with it. You might run into issues where the components you get don't have much life left in them but I think it will be worth it anyway

My server has a Pentium Pro. It is so old it predates the compulsory back doors.

Well you could kinda upgrade everything, but it feels like missing the point the point.
Put in new motherboard, new cpu, new ram and an ssd - all thats left is the old case

You can still buy ddr ram and pre lga775 CPUs. I'm sure you can upgrade it easily. Not hard to get a 771 converted to 775 and 4-8gb of ram for some 775 pc for example. What socket is it even running?

You know, you sound pretty cool, i'll tell you, i'm getting the computer for my little brother, I had one when I was a kid, I want him to have one too, but his first computer will have linux on it, not many games to play, so he'll be growing up with a real computer :), get used to the shell and learn about computers.

So you bought a case for 13$. That's alright I guess.

yeah.. you know.. I think the dude told me I can't upgrade because all he does is repair, i really don't consider him a computer enthusiasts, just refurbishing computers for the money..

the thing that really makes me think this is the place I live in, people don't really know anything about computers so he can say any price he wants, they can't tell if it's worth the cost or not

It's really not hard to upgrade shit as long as it's post pentium 3 these days.

If you're going to gut it, why not buy new hardware right away and skip the step where you end up getting stuck with ancient crap and a shit case?

if you intend to upgrade to really new hardware at ANY point, it's a money sink. Not to mention those slim computers have proprietary non-standard psu's and motherboard layouts, and usually only support low-profile pcie cards (gpu's for example) by default.