High fan speed, slower processor, occasionally will not boot

The error is related to SMC, but being so many the possible causes behind it, it’s a bit hard to give you a clear indication on what needs to be done, it maybe a simple part like a flat cable or a logic board component gone bad. Unless you want to bet money on some replacement connectors, the only alternative would be to have the Mac tested. If you have someone reputable into Mac repairs in your area that may be a reasonable alternative since several labs offer a no fix no fee approach, however, if you want to try a DIY repair, you may start replacing the I/O flat cable and trackpad flex cable and hope for the best.