Index funds mostly are damn close to the index they follow. Just Google “S&P 500 price” and change the time-frames and you can see the performance. Besides S&P 500 there is also Total US Market and some others. It depends on what funds are offered, but you should be able to click on the ones available and see their performance and the fees (labeled “expense ratio”, you want this below 1% or even below 0.1%).

You yourself can just transition to bonds (should also be in the list of offerings) as you get older.

> Is this something I can change easily?

For mine, I can transfer 20%/yr from one fund to another (but I can change future contributions with no limit), the limit isn’t something I knew it just was a pop-up message when I went to do it. Meaning if I have everything in A and want to fully tradition to B, it would take 5 years. But yours may be different options.

You can also contact whoever is in charge of your retirement.