Hi destinylove,
Regarding your credit repair questions
I don't have experience with Lexington Law - I'll let the others talk about them. However, I have heard just as many bad things about Lexington Law as I heard good things. From what I understand, all they do is have people (not necessarily attorneys) send debt validation letters and dispute letters.
The best scenario is to do the credit cleanup yourself because it's cheaper. You can get sample letters from this forum and send them yourself certified mail return receipt requested for about $4.00/letter. For example, if there is a debt that you want to pay, you can do a pay-for-delete letter, where you tell the creditor who owns your debt that you'll pay them if they delete the item from your report. If there is a debt that you don't owe (for example: you owed Credit Card A $100, but they sold the debt to Collection Agency B, and Collection Agency B is reporting that you owe $1,000), you can send a debt validation letter.
Regarding your bankruptcy questions
As you may already know, the bankruptcy laws have changed dramatically since the time your mother filed for bankruptcy. Even though you can still file for bankruptcy, you have to be stone broke to be able to discharge everything - most people have to file Chapter 13 bankruptcy, where you have to pay back your debts in a period of time. Plus, it's on your credit report for 10 years.
Regarding bettering your credit
You're on the right track - do everything in your power to pay your bills on time every month. As you pay your bills on time every month, your credit score improves.
Because of your score, don't get any more credit for now. You'll probably only qualify for sub-prime loans/cards, and from what I understand, FICO now counts that against you if you have a "consumer finance account" (translation: sub-prime) on your report.
Another thing that you can do is get your hands on every spare dime that you can and pay off the credit card. The lower you can get the balance, the better it will be for your credit score because your debt ratio will improve.
Another thing to do - if you have the resources, negotiate pay-for-delete deals with the creditors who own your debt.
Unfortunately, time is the best thing that's going to improve your score. As time passes, your older debts don't count as much against your score as they do now, and after 7 years from the date of last activity, they fall off your report.
Summary
For your situation, I would talk to a bankruptcy attorney and review your financial situation with him/her. Most bankruptcy attorneys provide a free consultation, and really good attorneys will sit with you and explain all of your scenarios (Can you file Chapter 7, or do you have to file Chapter 13? What will happen when you file Chapter 7 or 13? Are you better off not filing for bankruptcy and negotiating payoffs for the debt?). If the attorney recommends debt negotiation, ask if s/he will help you with the validations and pay for delete, and if they will, ask how much do they charge?