i just wonder how that changes the war without Argentina attcking Paraguay as wellFrom what I recall, Argentina was a bit less centralized at the time, and some of the northern provinces were friendly to Paraguay. Maybe if Francisco Solano Lopez doesn't manage to piss everyone off quite so thoroughly, you might see them lending some tacit (or not-so-tacit) support in a war against Brazil.
i just wonder how that changes the war without Argentina attcking Paraguay as well
Well, it certainly wouldn't be the War of the Triple Alliance at that point. Paraguayan forces had some success in the opening stages of the war against Brazil in Mato Grosso province; the Brazilians were far from their lines of supply. After that, the Brazilians sent a fleet up the river and there were a series of naval battles, which the Brazilians eventually won. I don't recall how vital Argentina and Uruguay's consent or cooperation were at this stage, but I think this was before they really became involved. However, if it looks like some of the northern Argentine provinces might back Paraguay, Brazil might be warier about provoking them with naval operations on the rivers--and in a land war, Paraguay might have a shot since it's much closer to the scene of the action.
Would it be possible though to have the Paraguayans assist Urquiza in the civil war and have Urquiza support the Paraguayans against Brazil and the Colorados as a measure of gratitude or whatever?The conflicts involving Brazil and Paraguay only happened after Argentina had declared itself on the Brazilian side, and such alliance is related to the civil war in Uruguay (as both Brazil and Mitre supported the Colorados there). If Argentina is pro-Paraguay (and you would need to replace Mitre for that) the odds are that the war simply wouldn't happen, or would happen over Uruguay instead.
Would it be possible though to have the Paraguayans assist Urquiza in the civil war and have Urquiza support the Paraguayans against Brazil and the Colorados as a measure of gratitude or whatever?