Careful about admitting you haven't spent much time searching the site. The pros here are not real patient with those who haven't tried on their own. :-p Luckily for you I've hung out a while, am not quite so impatient, and will summarize their general input on these things.
Yes, you can DIY it.
Ipe is available for all of the above.
5/4x6 decking with 1/8" spacing.
Not sealing allows it to turn gray, no problems with structural integrity in doing so.
With Headcote screws you predrill with a smart bit (basically a countersink bit sized for headcote screws)then put the screw in. You don't fill over the top of the screw. They're colored, so they blend in with the ipe. If you're letting it turn gray, so might want to use gray Headcotes.

Adding blocking to the joists would probably give you more added stability than sistering joists would.

ok, very good thank you weed. very nice summary.

But wonderering, I gather, every question from what I have seen probably has been answered or contained either in this site, or some other related site or referenece source. So really, nobody should be posting questions in here to resolve their concerns, issues or shortcomings.

For those that are impatient, maybe they should not have children, be married, have employees, start a business, own a home, render advice in forums, etc?

Personally dont understand why I would be punished for my forthrightedness, whereby, I would venture a guess,,95% of others act in similar fashion. Seems childish.

Just my 2 cents.

Thanks once again.

Jim, I just replaced my deck (lower and an upper) as a DIYer and did not find it very difficult. Ipe was a new wood to me so I spent some time researching it on the web and everything kept coming back positive. This site helped tremendously as questions and issues had already been addressed that I had not thought about. Using the search in this forum for "Ipe" (Bottom of page) will provide you a wealth of information. You will get answers to questions you did not know to ask. In addition, The pros here really help. Post progress pics and any specific questions and you will get all the help you need.

Here is my deck and you can see that I received "help"

http://ths.gardenweb.com/forums/load/porch/msg0602295520967.html

http://ths.gardenweb.com/forums/load/porch/msg072012207042.html

Here are very recent links that provide great info, there are lots more:

http://ths.gardenweb.com/forums/load/porch/msg0610144817578.html

http://ths.gardenweb.com/forums/load/porch/msg1221463624983.html

there were 675 links when i did a search in Ipe. a couple provide great recommendations on what tools you should have (18V Impact driver, drill, bo-wrench or equivelant, type of fasteners, what to avoid (search on hidden fasteners),
staining, railing etc.

you will also find good references on where to buy the material,cost,design considerations (joist spacing, ventilation) etc

Here's a few other sites I bookmarked:

http://www.decks.com/Calculators/Stairs.aspx?

http://www.stairways.org/pdf/2006%20Stair%20IRC%20SCREEN.pdf

http://www.mcfeelys.com/screws

Both Allison and Randy are going to be Pros themself after all the work on the house and the deck. The ol Salmon is not bad either.

I am not a big fan of the smart bit but others are.They just clog up and break too often for me,plus they are really slow.

It would be better not to double or sister any joist span for a lot of reasons.

5/4 ipe is spendy in several ways,the cost,extra trucking expence, job site handling,biger fasteners things like that.In the last 5 years I havent done a 5/4 job they are all 3/4'' x 6'' placed on the right 16'' on center joist system landing on the right foundation the result is the same in feel and long life. But if you really want it East Teak (800 338 5636 ) will gladley sell it to you.

Alum blasters are a good idea they look great with ipe,require 0 upkeep,install pretty quick and are less money than ipe plus half the install time.

Mrac you havent seen impatient yet so dont go crying about it. JonMon

Thank you, much appreciated salmon and John.

Boy, if any of you gentlemen worked in the CT area, I would probably hire you both site unseen. At this stage in my life, time is a bit more important than a few bucks,,so that is part of hemming and hawing whether to tackle it, and also, the unknown. Its a great pleasure sitting back after the fact, looking at your "picasso" on a nice sunny day,,and exclaiming, "yes I did that" - its very self-satisfying.

Thanks for your reassurances, and insight is priceless.

Jim

Just realized I goofed in my first posting. John's right, recommendation on deck boards is 1x6, which is what I'm using. Guess I just had a brain fart when I was typing.