Perhaps I should expand a bit...
NiCads are still available, but harder to find. Likely the ones at the local hobby shop have been sitting there a long time. Many times they have been supplanted by Nickel Hydrides (NiMh). For the same size pack, you can use the same old NiCad charger you always used. But there is the rub - both may have greatly increased in capacity, so a "wall wart" type charger that charged overnight, may now take days. Just went through this with a friend that wanted to revive his old gear. So prepare to do a bit of Internet searching if you are looking to replace existing. to match pack physical size and capacity, particularly the ones in the TX. Moot point if you will be starting off with a new radio system.
Don't confuse LiFe (Lithium Iron) with LiPo (Lithium Poly). LiPo's run at a higher voltage, and when used in conventional, older flight gear, may be too "hot" for the electronics. Electric planes have that stepped down from their ESC. Or you may need to put a voltage regulator in line if using them in a glow plane. LiFe's are not as "hot", although are bit higher than NiCads. A typical 2S pack runs at 6.6 v, which is a bit high for nominal 4.8 (old NiCad powered) flight packs, but most do just fine with it. Not much different from the old days, when many of us used 5 cell NiCads to get a little more "oomph" out of the servos.