Just finishing up doing the disk conversion so I can definately say from experience piecing it together looks like a cheaper alternative, and it appears that way. What I didnt take into account was all the little things the kit includes that I had to buy in addition to everything else. Buying parts a little at a time will help soften the blow to the savings account, but if I were to do it again I think I would buy the kit.
First of all, welcome to the site iloveLucy. I highly recommend the mini subframe kit by CPP, definitely the best bang for the buck. Do a search for it and you'll find a ton of information on it. Rack and pinion steering is an option if you go with the Church Boys setup. I would have gone that route if it was available when I did mine.
As for disc brakes, I purchased a set of caliper mounting brackets online, picked up a proportioning valve from the wreckers, and got the remaining parts from my local NAPA or Canadian Tire. It cost me about $500 (Canadian) for my disc conversion.
Lots of options available for what you are wanting to do. If you go with a aftermarket front clip, it should include front disc brakes. You can PM me if you want information or want to discuss options.