Database migration and website recoding

I have a website which is running on ASP and uses Access databases. Frequently the website is out of service because of exceeded system resources error which I my hosting company told me is owe to connections to the database left open by the script. I would like somebody to : EITHER -fix this problem , by finding the loose end in the script OR -recode the whole website from ASP to PHP using the existing layout , and migrate the existing database to MySQL It is important to point out that currently the site is used by my customers so any work must be done in the background without affecting original site's functionality . Moreover I require that any work carried out comes with a guarantee.