Is there a way to replace or swap leaders? Replace or swap UA, UU, etc?
Example: I want to play as England but I want the ability of the Shoshone.
Is this possible?
Sorry for dumb question; just curious.
Yes, and this should be an "easy" one.

But since "easy" is relative to your modding skill, and you appear to be new to the forum, I will try to point you in the right direction first before throwing a bunch of code at you.
First, go read
Kael's Modders Guide to Civilization V so that you have a basic understanding of how to use ModBuddy to create "simple" mods. Then read through what I have so far in
The Newbies Guide to Modding Civilization 5. I haven't completed it yet, but it should have enough to get you started.
Basically, what you will be interested in doing is something like this:
Code:
<GameData>
<Civilization_Leaders>
<Update>
<Where CivilizationType="CIVILIZATION_ENGLAND"/>
<Set LeaderheadType="LEADER_POCATELLO"/>
</Update>
</Civilization_Leaders>
</GameData>
Now, keep in mind I haven't tested this code. I think I have all the syntax correct. I'm also not sure if there is anything that might cause bad game behavior with two civilizations having the same leader. I suppose you could do the following to prevent that problem, but I don't think it's necessary.
Code:
<GameData>
<Civilization_Leaders>
<Update>
<Where CivilizationType="CIVILIZATION_ENGLAND"/>
<Set LeaderheadType="LEADER_POCATELLO"/>
</Update>
<Update>
<Where CivilizationType="CIVILIZATION_SHOSHONE"/>
<Set LeaderheadType="LEADER_ELIZABETH"/>
</Update>
</Civilization_Leaders>
</GameData>
If you still want to play as Elizabeth but with Pocatello's UA, then you would do something like this:
Code:
<GameData>
<Leader_Traits>
<Update>
<Where LeaderType="LEADER_ELIZABETH"/>
<Set TraitType="TRAIT_GREAT_EXPANSE"/>
</Update>
</Leader_Traits>
</GameData>
If you just want England to have the Shoshone Pathfinder, you could do something like this:
Code:
<GameData>
<Civilization_UnitClassOverrides>
<Row>
<CivilizationType>CIVILIZATION_ENGLAND</CivilizationType>
<UnitClassType>UNITCLASS_SCOUT</UnitClassType>
<UnitType>UNIT_SHOSHONE_PATHFINDER</UnitType>
</Row>
<Civilization_UnitClassOverrides>
</GameData>
This would give England the pathfinder
in addition to it's other uniques, which might not be what you want.
NOTE: The Row tag is used here because we are adding a new unique for England that didn't already exist, as opposed to changing something that already exists. This is covered in Kael's guide.