You should keep the T-54 and train up another crew for the T-62. The T-54 is too good to just ditch.T-62A is researched now. Another tank on the 'to buy' list. Does the t-62A have any ammo rack or fire problems? Current T-54 crew has 100% Repair and 99% Fire Fighting skills. Its an old crew from way back and I think I need to reset their skills for the T-62A but not sure.
I'd go 6th sense + BIA/Repair first. If you don't do clan wars, I'd get camo over repairs as T-62 has pretty decent camo like all russian mediums and it's more important to stay hidden in pubs.
Sorry don't know much about fire/repairs in the 62A, but I haven't seen people complain about them much and it shouldn't be too different from the 54.