Manual transmission has suddenly become very difficult to put into 1st & reverse

does the clutch pedal feel different. if it does you may have a bad cable or a failing hydraulic system. if the clutch feels ok then you may have a linkage or internal problem. bring it in for a free inspection and estimate.

Check engine light is most likely a different issue but I would inspect the clutch hydraulic system, look for leaks, check the fluid level, perhaps the clutch master or slave cylinder is failing.