I suggest that you get an experienced DWI for these charges. A second time DWI carries with it the possibility of a mandatory minimum period of 30 days in jail. There is also a ling license revocation period depending on the circumstances of the case. You need someone on your side to help you minimize those consequences, deal with your license, a d keep your job.
The fees folks like myself charge vary depending on who you talk to. Set up a consultation and see if you can work with one of us to make this situation affordable for you. A lawyer in a situation like yours is worth the money.
You can call me at 612-223-7286 if you'd like a free consultation.
The answer to most of your questions depends on the specific facts of your case. It is best to speak with an attorney directly. As for the fees, that may vary depending on the attorney. Most criminal defense attorneys offer a flat rate fee; however, others may offer an hourly fee or payment plan. The only way to find out is to contact someone directly. Even in cases where jail may be mandatory, there are alternative which can be explored to avoid the jail time.
Each person must decide for themselves what they really "need." Can you afford to lose another DWI case? With a prior, you must know how expensive that was, when you total all of the costs of a DWI over a five year period. A DWI defense law will cost much less. I recommend that every person arrested for DWI fight both the administrative drivers license revocation case (within the 30 day deadline); and the criminal-DWI charge. Typically, a Public Defender will only be able to help with the second of those two. You may want to call a DWI defense lawyer to discuss the many issues and questions that come up in these situations.
These are all great questions that deserve an answer prior to hiring an attorney. However, they are very specific and really require you to speak with an attorney or attorneys directly to get your answers. With regard to your question about whether you should hire an attorney - I strongly suggest, especially since this is your second offense, that you indeed retain an attorney to assist you for various reasons.
In no way am I offering you legal advice, and in no way has my comment created an attorney-client relationship. You are not to rely upon my note above in any way, but instead need to sit down with counsel and share all relevant facts before receiving fully-informed legal advice. If you want to be completely sure of your rights, you must sit down with an experienced criminal defense attorney to be fully aware of your rights