new and very keen

Hi, im new to this site and am hoping to try and get some help with my truck problem . It started last winter but hasnt really got any better if not worse . Firstly im not what you would call a great mechanic so if anyone can help you may have to explain in detail if you dont mind . Ok here we go , last winter my truck had trouble starting in the mornings ( mitsubishi l200 warrior ” 02 ” plate) it eventually started then rest of day it was fine . I have changed the glow plugs for new NGK ones and changed the glow plug rail but the problem still wont go away . When i turn the engine over it its like it just wont fire up . Im not sure if it could be the glow plug relay but i dont really know how to check it . This may all sound a bit dumb and simple but it really is starting to get me down . Any advice or help would be much appreciated .Many thanks.