If I stir my wine after the first racking, won't that stir up all that sediment? Will that give the wine a bad taste and will it reduce the ABV? I don't want to do either one. Obviously this is my first time making wine. I racked it from the primary to the carboy 4 days ago.
How much sediment you'll disturb depends on how you stir. Usually you try to get the wine to clear (i.e., get rid of the sediment), as wines (especially white and rosé) are supposed to be clear. Sediment will probably also have a negative effect on the taste (e.g., yeasty).
Stirring won't have an impact on ABV.
Any CO2 the yeast has produced during fermentation probably has already escaped through the airlock.
Usually, degassing wine is done prior to bottling, often after 2 rackings or more.
The fact that you racked your wine means that you left most of the sediments in the primary, so stirring the secondary won't disturb any sediments, they have not settled yet. The bad taste and loss of ABV will only occur if your wine gets infected, so make sure that you sanitize your spoon or any other instrument that will touch your wine.
I have seen wine kits that instruct to stir before the first racking (which means that sediments are transferred to the secondary). However stirring (mixing the sediments) is not the same as degassing (removing CO2). Later, the sediments are left behind after the second racking.
If your wine kit recommends stirring, follow the procedure but sanitize your equipment carefully. Personally, I would degas my wine only before bottling, which I normally do after 4 weeks, not before.