Tags, my BX came with the block, so installing the loader was no harder than rotating tires on my truck or something akin.
I'd have to read the installation guide for the joystick, block and lines to comment on the degree of difficulty. That said.
$450? I'm waaaaaaay too cheap to spring the money for the hardware and then spring another $450 for the installation labor. I have a well equipped shop, I have the patience of Job in doing jobs like this. I'm semi retired and have the time, although surely, it cannot be a week long project. I'm quite sure I've tackled much more difficult jobs that this. No offense whatever to the guy at the shop who does this install, but I've been doing mechanical work for a long time. When you've got more time than money, you do this kind of stuff, I guess.