Paleo is a brandname for a particular version of an ancestral diet.
It's pretty good but many people have problems by going too low-carb.
(Our ancestors would have relied heavily on roots and tubers and would have valued carbs but would never have access to the (high) quantity and (low) quality available now.)
There are so many paleo sites that it can get a bit confusing as to what is and what isn't 'legal'.
The number of paleo cakes and treats is truly staggering as all the sweeteners are 99% the same (sucrose, frucose and glucose).
You should avoid those for the first few months, along with any commercial milk substitutes.
I think it is best to look at it as a framework for determining what food is right for me (you).
Firstly eliminate anything that isn't food, this means ALL 'food-like products' so everything manufactured is out (with a slim possibility of reintroducing small amounts of some of these foods later if they are tolerated)
Eliminate all processed foods, sweeteners, grains and seed oils is an absolute must too begin with.
I would recommend looking at the the GAPS introduction diet[1] (and full GAPS if it suits you), the "perfect health diet"[2] and reading up on the 'autoimmune protocol'[3]
What works for you will (probably) be somewhere in that triangle.
[1] Gut and Psychology Syndrome Introduction Diet
http://gapsdiet.com/INTRODUCTION_DIET.html
This is a great diet to bring symptoms under control (i've read more positive anecdotes than negative for what that's worth).
Many may find the GAPS diet too low carb and too restrictive long term, but as an intro to bring gut bacteria under control and restore digestive function it is well worth a try.
There are many who find low-carb diets to be fine but some people have health problems that may take a while to manifest.
I would say it is ok to go gaps to get things under control and then introduce tubers and maybe white rice after that.
GAPS is very similar to low carb paleo with more emphasise in probiotics and restoring healthy gut function
[2] Bowel Disorders, Part I: About Gut Disease (part 1 of 4)
http://perfecthealthdiet.com/2010/07/ulcerative-colitis-a-devastating-gut-disease/
These diseases probably develop through a hierarchy of causes:
-Food toxins damage the intestine and make it leaky to gut bacteria and bacterial proteins.
-Malnutrition impairs the immune response to toxins and slows the healing of intestinal injuries. This makes the intestine even more leaky and damaged.
-Damaged immunity allows bacteria to penetrate the gut mucosa and infect intestinal cells, and to enter the body and create systemic infections including intracellular infections of immune cells. The immune response to these infections creates an inflammatory environment which makes the gut even leakier. The infections also weaken the ability of the immune system to heal the gut.
-Entry of toxins and bacteria into the body leads to autoimmunity. Food toxins conjugate with human proteins and provoke antibodies against the human protein; bacterial proteins that are ‘molecular mimics’ of human proteins engender antibodies that strike both the bacterial and human proteins.
-Autoimmunity leads to further damage to the gut and to other tissues, like the thyroid, which are important for immune function and wound healing. Hypothyroidism, for instance, promotes disease progression.
-In its early stages, development of the disease may be accelerated by a long course of antibiotics or an infection that causes severe diarrhea. These kill healthful gut bacteria and facilitate their replacement by pathogens.
[3] The Autoimmune Protocol
http://www.thepaleomom.com/autoimmunity/the-autoimmune-protocol
I think this is still very relevant even though crohn's (probably?) isn't an autoimmune disease. It is still a damaged immune system that does not preform it's functions well enough to maintain health.
Genetic predisposition to autoimmunity makes up about one third of your risk of developing an autoimmune disease. The other two thirds of your risk come from environmental factors, which include: diet, lifestyle, infections (both prior and persistent) exposure to toxins, hormones, weight, etc. While you cannot control your genetics or whether or not you had mono as a kid, you do have an immense amount of control over your diet and lifestyle (and the extent that these affect hormones and weight and even toxin exposure). By removing the foods that contribute to a leaky gut, gut dysbiosis (the wrong numbers, relative quantities, or types of microorganisms typically growing in the wrong locations in your gut), hormone imbalance, and that stimulate inflammation and the immune system, you can create the opportunity for your body to heal. By addressing important lifestyle factors and changing your focus to eating nutrient-dense foods that support optimal gut health (and optimal health of your gut microorganisms), that restore levels of important nutrients and provide all of the building blocks that your body needs to heal and properly regulate the immune system, that help resolve inflammation and support organ function, you create an environment in your body conducive to healing.