A couple of issues

That would depend on how many miles, how much work is needed, and what was done to the car previously.

On a recently acquired car; I like to spend as little money as possible to get it road worthy again. Then go from there, to determine how much additional work is needed and it's priority. I may end up flipping it, to a mechanically inclined friend with the laundry list and priority of each item. These are project car guys. They don't do it to turn a profit, like me. I've got about a dozen of these guys on speed-dial. They like me, because I give them a good deal with a laundry list of things that need to get done. I've already done a through once-over and shake-down for them, so no surprises.

Mistakes happen, as long as you learn from them and don't repeat them - That's all a part of LIFE...

Good Luck.....

 

The difference between a pair of control arms and one control arm shouldn't be mission critically large but if it is by the one that's needed it has the bushings in it and all of that so you're just pulling bolts putting it in you need a long bar and figuring out how to put it in and pull on it while you pull the or put the hardest bolt in it can be a real pain but other than that that should do it I don't know whether you need a new lower ball joint and all that other stuff or not If the car was smacked or something happened I have no idea but you want all that suspension stuff to be pliable and working as exposed to You don't want a lot of clunking and all that kind of funny business going on.

 

I would hope grinding while turning is not your ball joint but that's another whole issue with your steering wheel sitting like it's sitting 120 point inspection I don't know if that includes putting the alignment heads on the wheels like they're aligning the car I'm sure it does not so what you need is a person to put the alignment heads on all four wheels and see what the problem is not 120 point inspection Why is the lower control arm bad? Is this thing been curbed or something?. 120 point inspections fine like if it's near free I mean you should be able to get well I'm not even going to go there anyway yeah I would go to a front end shop or alignment place a place that's known in your town to do alignments for very reasonable like where I live it's 50 bucks instead of the normal 80 to 120 they will set the car up put the heads on it and align the car if they can align it they'll tell me why they can't because such and such and so and so needs replacing boom.

 

Gen 3 has funnier control arms than my generation too I think I've got both cars here about to go out and look for some reason people seem to be able to tear them up pretty easily on the generation 3 or I hear people talk about replacing them for bad bushings or whatever the case may be that goes wrong in the things on four or five generation twos we haven't had to touch the lower control arms We put ball joints front hubs brakes and the like struts but no control arms bushings aren't worn out nothing that just hanging there

 

How many miles are on the car? That's important.

It's not likely it needs control arms, UNLESS, either or both have been damaged from
hitting something in the road. How does the car drive?
Same with the ball joints. These things last a LONG time.
"IF" you need too replace the control arm, you "should" do both at the same time.
You can buy them yourself and replace them. A little tricky, you can't force them.
And don't really need too, it's just getting them at the correct position to remove and install.
Watch at least 10 different video's on how to do them. So you'll have a good idea on how
to do them.

Maintenance will depend on the mileage. 100,000 miles is where everything starts.
Coolants, transmission, spark plugs.... Guide pins for the rear (and front) need to be cleaned
and regreased sooner.... You can do a search and find what needs to be done.

Also, and most important, the egr system NEEDS to be cleaned at about 100,000.
A little more work, but very doable.

As for "that" place, I wouldn't even waste breath on saying that place. Going to a shop
the KNOWS about the Prius and how to work on them is your best bet.