If you have earned income of £25,000 and the State pension of £580 per month (this is normally paid every 4 weeks) so should provide an annual income of £7,540 your total income is currently £32,540.
Your personal pension will allow you 25% tax free (£38,000/4 = £9,500) and the other 75% will be taxed at your marginal rate. In your case the additional £28,500 will push you into the higher rate tax threshold (40%) as your total annual income will be £32,540 + £28,500 = £61,040. Not all of the £28,500 will be taxed at 40% but approximately £10,000 will be and the rest will be at 20%.
If you use flexi access drawdown you can take funds from the pension in stages. For example, you could just take the tax free cash and leave the rest in the pension, or you could take the tax free cash and 'some' income but being careful not to go into the higher rate tax bracket. If you took the pension in stages over a couple of tax years then you would avoid the need to pay any higher rate tax.
Some pensions offer drawdown, some don't. You can always switch pensions if it does not and you should seek independent financial advice to do this, the adviser can then explain drawdown along with all your options.
Please note, pensions offer excellent legacy planning benefit's and protection from tax whist retained. If you have separate cash/investment's you may want to utilise those first.
An IFA will be able to recommend a suitable strategy for you.