I set the temp to 350 and press start. After an hour the tempo has only reached 145. If I change to broil I can get the temp up to 350 and then change to bake. Is the bottom element bad and needs replacing or is there a problem with the temp gauge?
I would access the bottom element, disconect it and test with ohm-meter (multi-meter).
You are hoping for zero (or very low) resistance across the contacts you just unplugged - resistance is measured in ohms (greek letter omega).
If resistance is very high or infinite , the element is burnt out.
Seems the logical place to start.
Does the unit stay in preheat?
If yes then odds are that the oven sensor is OK.
If the unit shows it is ready then it is probably a control problem.
A model number would be helpful.
If you check the bake (lower) element be sure to unplug the unit when doing this.
Many units have one side of the element always hooked to power so they must be unplugged or the breakers shut off.
Unplugging is the safer of the two.