Will I need an expert to prove malpractice has occurred?
Almost always, yes. In order to establish malpractice, it will be necessary to define the standard of care in the community for a professional handling a similar matter. Lay people do not have the necessary education, experience or skills to act as a professional -- or to gauge what a professional is supposed to do or refrain from doing in a particular situation.
In order to determine what should or should not have been done in your particular circumstances, someone with the requisite education, experience and skill would be needed to establish what the standard of the community is. Many malpractice lawsuits are won/lost based upon the effectiveness of the expert.
Experts should always be hired by your attorney, to maintain confidentiality and retain your rights. The leading site used by attorneys to find expert witnesses on the Internet is ExpertPages.com.
If you have sustained losses due to the negligence of a professional, you should seek the advice of a malpractice attorney, and do so quickly to ensure your rights are preserved.