I am Linh, Top Joomla Developer from Vietnam.I have worked and had much deeply experience in
upgrading Joomla site from 1.5 or 2.5 to 3.4 [latest version] , secure it [ install Firewall to prevent hacking] If you want to ensure, please check my reviews on related jobs in my profile.
What step I will do for you
+ Install new Joomla Fresh Latest version.
+ Move contents, articles, users, media,.. from old site [ database] to latest version
+ Clone new fresh template [ no use old code] and make sure it is the same with old site[ if you want]
+ Make sure all SEO Links work greatly as old site
I guarantee
+ Clean code, native responsive layout, works well with all mobile and tablet device
+ Full document and guide after moving it to production site
+ Have warranty you at least in 3 month for supporting free
+ Good in English and keep to reply you within 1 or max 2 hours
I really want to work with you on this project so looking forward to starting now. Thank you for your attention
Developer
Linh