Fix My Google Analytics Set Up!

I have a Joomla/Virtuemart e-commerce website and am having a lot of trouble with my Google Analytics data. I suspect that the Analytics was not set up correctly. Some sales/orders are registered as TRANSACTIONS and some are not. Some are registered as GOALS and some are not! I have not been able to determine a common dominator for which sales are recorded as transactions or which as goals. The last person to look at this problem for me unfortunately made it worse! Now when I get a sale and IF it is captured as a transaction, the one sales appears as 2 transactions with double the sale dollar value! It's a mess and I need a GOOGLE ANALYTICS EXPERT to fix this for me. Please DO NOT BID if you are not a a GOOGLE ANALYTICS EXPERT. My budget is very limited so I need someone who is capable of identifying the problem quickly and fixing it even quicker! Many thanks :)