It sounds like you neither battery on had so one will need to be purchased. IMO the LiFe is the preferred battery to use. It (LiFe) is less fussy about state of charge and stores better. Both chemistries are fussy about over discharge but the LiFe may be a bit more robust than the LiPo in that respect. It you are handy then there are on line stores where you can purchase individual cells and build your own pack. Both chemistries need to be balanced charged so no difference there. A charger that will charge and balance the respective chemistries is needed. "Any old" charger will not work as both need to be charged to a specific voltage and over charging can be a disaster especially with LiPo.
I'm switching over to LiFe for all my flight packs as the old NiCad and NiMh packs reach the end of their life. I also plan on a LiFe for my starter this winter.
Ken