The monovalve could help with the flaky heat. Mine would come and go. The monovalve diaphragm seemed to help. Someone posted a pictorial how-to(diesel 126) awhile back. Same deal.
Monovalve how-to at this URL:
For the blower, pop the hood - drivers side near firewall - fuse box. Open it up. Look at #5 fuse. If this blows, you loose the blower. Even if the fuse looks good, replace it or at the very least, reseat it, but beware - these ceramic fuses are WEAK. Reseating could break the fuse. I suppose the brushes in the blower motor could be worn. Try the #5 fuse first. Quick & simple if it solves your problem; however, I kinda doubt it will. Sounds like you've been loosing this on & off. Fuses usually are not an on/off affair. Thought I'd mention #5 anyway. Mine has blown twice in the 6 yrs. I've owned the car.