If a engine has E85 capability, what changes are needed to the engine? Is there more hoses, solenoids, condensers, etc to further fill up the engine compartment?

to my understanding it has differnt valves and gaskets and fuel lines that can handle E85 with out diterating those things mentioned. I dont know really no how it works tho.

Yes as capriceman said ther is no modifications needed if the car is e85 compatable it is designed so you can run e85 and run gasoline as well if you were somewhere they didn't sell E85 so you are set to fill up.

There is nothing extra in the engine or under the hood , I read they just get different injectors and stainless steel fuel lines and gas tank

Yep, that's it. E85 is more corrosive to steel than regular gasoline, so the fuel delivery system needs to be made out of a different material.

In the case of the older S10's & Sonoma's:

Plastic was used for fuel lines, as well s/steel. The engine itself did not use different gaskets

From what I've seen parts wise, like y'all have said, you get stainless lines and reinforced plastic lines, and if memory serves correct, the fuel pump itself is different internally, otherwise you wouldn't know the difference between an E85 capable vehicle and a regular gasoline vehicle unless you got ahold of the paperwork.

All future GM E85 engines will have a yellow gas cap so that's an esay way to know.

According to a friend of mine, the newer Crown Vic/Grand Marquis' are E85 compatible, and they had to put harder pistons in for it. The old style were too soft and the high octane would burn holes in them eventually. But yeah, most vehicles the company just has to upgrade gaskets & fuel lines & such.

All future GM E85 engines will have a yellow gas cap so that's an esay way to know.

before that they put a sticker inside the fuel door saying that you can use E85...my suburban has the sticker and so did my mom's old caravan that she had for work.