Secure website and ensure stable platform

I need a coder to have a look at the code on my site and firstly upgrade the code not to use magic quotes. also need to secure vulnerable areas of the site such as forms using SSL. there is currently a loophole in the code that is allowing hackers to change code on the site that needs to be secured. this has to be identified and eliminated. the site was recently optimised for speed and performance but now we have to ensure that security has solid. We dont have a huge budget for this site as we already paid for the development of the site and this is now already over budget. we need someone who has experience in this field and can fix this problem efficiently and within a realistic budget.