You can certainly try negotiating with the IRS yourself, but if you need assistance, you will have to pay for it. If you accept the IRS offer of $300 per month, your interest and penalties will most likely keep accruing until the entire amount has been paid.
The information you obtain at this site is not, nor is it intended to be, legal advice. You should consult an attorney for individual advice regarding your own situation.
Unfortunately, to hire a professional it will cost you money. At $300 per month, the balance will continue to grow since this is not enough to pay the interest and penalties that will accrue on the unpaid balance. You could consider bankruptcy, or an offer in compromise. However, these will require the help of a professional. See if you can work out a payment plan with a tax professional.
Any individual seeking legal advice for their own situation should retain their own legal counsel as this response provides information that is general in nature and not specific to any person's unique situation. Circular 230 Disclaimer - Advice given in this response cannot be used to eliminate penalties with the IRS or any other governmental agency.
If you can afford to pay the $300 per month, you may want to agree to that sum. If you think you qualify for an "offer in compromise", which can reduce the amount paid, you will need a tax attorney or accountant, and this will cost money. Be very careful of so called "tax relief" sites, as they will take your money and not do anything more than you could do yourself.