You can recover the loss of use or the reasonable rental value of the same or similar vehicle in the lawsuit just by alleging it as an element of damages, assuming you can prove negligence on their part in the lawsuit.
That would normally require calling witnesses that can testify as to the amount of time the car was in the shop, the cost of the rental, etc. Usually that would be a witness from the body shop and then one from the rental agency.
As to wages, you can only recover the lost wages directly attributable to the damage but not the lost wages accumulated due to trying to recover your damages. As an example, if you were on your way to work and the car was wrecked to a degree that you couldn't get to work then you would be entitled to your wages for that day. If you have to take off work to pick the car up then those wages would be recoverable as well. However, the law doesn't have a provision in it to allow for you to recover for the time spent trying to get them to pay, etc. You can ask for it in the lawsuit and offer testimony about it but that is not an element of damages the law allows you to collect, although many of us feel it should be.
A lawsuit generally follows this process:
1) File the petition in the court with jurisdiction and venue. The court with jurisdiction and venue is usually where the defendant resides or has their place of business. You also have to look at the amount you intend to sue for to determine what court is correct
2) When you file the petition with the clerk of courts you will pay the filing fee and also ask for citation to be issued and service to be done. The clerk doesn't serve the papers so ask them if you have to take them to the sheriff's office for service or if they will do it. Just follow their directions as to that.
3) The sheriff will serve the defendant with the lawsuit.
4) The defendant will file their answer.
5) You can then do some discovery if necessary but you will need to check with the clerk and ask if your court allows discovery. Some small claims courts do not.
6) After that the next step is to set the case for trial.
7) During the trial you introduce your evidence and they introduce their's.
8) The judge renders a judgment and a written order is entered.
That is the basic process of a lawsuit.