Restrictions and modifications?
Not too sure what you mean by restrictions but as far as modifications go it really depends on which kit you go with.
If you go with coil overs then you will need to grind the tops of some brands of struts to get the coil overs to slide on.
Also with coil overs, you will have to relocate where your brake line attaches to your frame. It will hit when you turn the wheels. Also you will loose some inner clearence with coil overs as well. Thus you will not be able to run as much backspacing on your front rims.
Also be sure that if you get a K-member, be sure get one with the factory
geometry unless you specifically want to change it so you don't run into clearence issues.
I have heard of hit or miss with D&D from people on this site but a friend of mine gave them a try and it was a BIG MISS.

I do not recommend them from personal experience.
I used a UPR kit but don't really recommend them either due to bad business practices and VERY POOR customer service. I got it for free so I tried it and it fit fine.
If I had to buy I would look for some one else.
Good Luck.