The civil rules of procedure and the rules of evidence put requirements on the types of documents you can provide as evidence. You will want to get an affidavit from your doctor which states that he/she treated you, that they think the injury was caused by whatever you are suing the defendant for, and that the amount they have charged you is fair and reasonable. The affidavit needs to be signed in front of a notary.
For any other documents you are using, you will need to be able to "authenticate" them. In other words, you will have to show that they are not fake documents. The easiest way to do this is to have the office from which the documents came from fill out a business records affidavit. You should be able to find a form on line for California. If the records are from your personal records, then you will need to offer testimony
at the new trial
to state where the records came from and that they are genuine and true copies.
Other than these issues, since you are representing yourself and since this is an appeal from the small claims court, the judge will help you along.
As far as hiring an attorney, you could call around and see if you could find someone to accept this low of a fee. However, standard attorneys fees in California are around at least $200.00 per hour. When you are looking for an attorney, you will want to avoid large law firms. Look for smaller firms if you want to go down the route of hiring someone. But don't be afraid to represent yourself.
As your case is a personal injury
case, you are likely asserting your claim as a "negligence" claim. Therefore, you will need to prove (1) that the defendant had a duty to you (ie that whatever the defendant was doing which caused your injury was something that they had to take reasonable care in doing), (2) that the defendant breached this duty (you need to show what the defendant did wrong), (3) that the breach of duty caused your injury (you have to link the wrongdoing to the injury), and finally (4) you have legally recognizable damages (medical bills, lost wages, pain and suffering, disfigurement, future medical bills, etc).
You need to be very organized, so you should probably right out all the points that you want to establish and make sure to ask for each and every possible thing that you can be compensated for.
Please let me know if you need any further information and if not, good luck in court and I hope you win the appeal.