Auto zone has a Quest 134a with 2oz of sub zero booster and with a gauge for $26.99

http://www.autozone.com/autozone/catalog/accessories/accProductDetails.jsp?counter=5&categoryDisplayName=Air+Conditioning+Refrigerant+and+Accessories&fromString=search&itemIdentifier=532242_0_0_&productId=532242&sortType=&parentId=1308-10&filterByKeyWord=FREON&categoryNValue=101308&navValue=101150&fromWhere=&itemId=1150-10&displayName=17+oz.+of+R134a+and+2+oz.+of+Sub-Zero+A/C+booster+with+shelf+saving+dispenser&store=5282&skuDisplayName=17+oz.+of+R134a+and+2+oz.+of+Sub-Zero+A/C+booster+with+shelf+saving+dispenser&brandName=Quest

It says synthetic and no tools required. I can find out how much is in there now using K6JRFs method. Do you think it is safe for me to try myself.

I like to be able to familiarize myself with my car by doing simple DIY things myself . Also if it does not take it all , can I save it for future use ?
Is Quest a good brand