The temperature dependence of conversion of He(2\sp3S\sb1) metastable atoms to He\sb2(a\sp3Σ\sbspu+) metastable molecules in the three-body reaction He(2\sp3S\sb1)+2He(1\sp1S\sb0)→He\sb2(a\sp3Σ\sbspu+)+He(1\sp1S\sb0) has been investigated over the temperature range 65K-700K. This reaction is thermally activated as a consequence of a long range repulsive barrier in the He(2\sp3S\sb1)−He(1\sp1S\sb0) interaction potential. The data reveal that there are two reaction channels with distinctly different activation energies. The temperature dependence of the measured rate coefficient k\sbs(T) is accurately described by k\sbs(T)=[87.4 T exp(−750/T)+4.1T exp(−200/T)]×10\sp−37 cm\sp−6sec\sp−1. The first activation energy, 750 ± 70K (63 ± 6meV), is equal to the known He(2\sp3S\sb1)-He(1\sp1S\sb0) repulsive barrier height. The second activation energy is 17 ± 2 meV. The temperature dependences of the rate constants for collision-induced mixing among He(2\sp3P\sbJ,m\sbJ) levels, and for conversion of He(2\sp3P) atoms to He\sb2(b\sp3Π\sbg) molecules in the three body reaction He(2\sp3P)+2He(1\sp1S)→He\sb2(b\sp3Π\sbg)+He(1\sp1S) have been investigated over the range 1.4$\sim$300K. The measured thermally-averaged cross section for He(2\sp3P\sbJ,m\sbJ) mixing in collisions with ground state helium atoms are described by the function σ\sbpm(T)=(4.4+20.6/T\sp1/3)×10\sp−15cm\sp2, and can be understood in terms of Langevin theory. The measured rate coefficients for the three body reaction exhibit a strong inverse temperature dependence, k\sbp(T)=(0.04+2.18/T)×10\sp−30 cm\sp6⋅s\sp−1, which suggests that, unlike conversion of He(2\sp3S\sb1) to He\sb2(a\sp3Σ\sbspu+), there is no activation energy required for this reaction. A magneto-optical trap for helium 2\sp3S metastable atoms has been designed and constructed, utilizing superconducting magnet gradient coils and a Ti:Sapphire ring laser for pumping the helium 2\sp3S-2\sp3P transition. He(2\sp3S) atoms are produced by a weak discharge in helium gas at temperature 1.3K. The discharge products flow through an orifice into the trap cell, where the He(2\sp3S) atoms are trapped and ground state helium atoms are rapidly cryopumped by zeolite pellets that cover most of the cell bottom. Preliminary experimental results suggest that $\sim10\sp6$ atoms are trapped, with a trap lifetime of about 0.2 sec limited by He(2\sp3S) - He(2\sp3P) Penning reactions. Ultimately, it is estimated that a substantial number of atoms can be trapped and cooled for much longer times in a near-perfect vacuum. Measurements of decay times of the trapped atoms should yield rates for \sp4,3He(2\sp3S) - \sp4,3He(2\sp3S) and resonantly-enhanced He(2\sp3S) - He(2\sp3P) Penning reactions in the ultra-cold quantum regime, and perhaps the He(2\sp3S) natural lifetime.