I'll start with the boots. There are a number of places on the web to get these now a days. I got mine from Champion Attitude Boots also known as CA Boots. Another good place is EBAY. Order these in your regular size. When you first get them they will be almost impossible to get on and just as hard to get off again but comfortable enough to wear. Eventually you'll stretch the neck out enough that getting them on and off won't be a problem. Don't worry about ripping the tabs, that's what they're there for, to help you get the boot on.
If you plan on being in costume for any length of time, (and you should be, why else did you buy it?) I would highly recommend getting some gel inserts. After 8 hours at a convention my feet were dead and I resolved to get some. Now I don't have a problem.
The shins I pretty much stuck together. Some velcro down the front and back hold them together. Recently they've been coming apart at the back so I may need to shim them in the future. The sniper plate on the left leg was riveted on. I put some electrical tape on the back to keep the rivets from tearing up my undersuit.
The thighs have gone through multiple iterations. I've tried numerous ways to attach them to my torso, trimmed both the top and bottom, and added shims in the back to widen them. Originally glued together with PVC glue I used Plastic Welder to attach the shims and straps. You can see in the pictures where I had multiple places where the strap was attached. I moved it farther to the outside of my leg so that now the straps are covered by the drop boxes on my belt. To attach the thighs I wear a web belt under my armor and attach them to that.