Sorry to hear of your loss. May the Lord receive Richard into His eternal light.
A couple of thoughts from someone who has walked that road before:
-The only way to walk through the valley of the shadow is to put one foot in front of the other and keep repeating the process. Step by step, as hard as it is sometimes, is how we get through to the other side where we can experience our own peace and light again.
-As hard as it is to believe right now, it gets better over time. The hurt and pain gradually recede to leave the laughter and joy in memory fresh.
-Don't let anyone tell you how (or how long) to grieve. Each of us comes into this place with our own unique experiences and personality, and each of us walks the walk in our own way. At the same time, let others who have been there walk with you when they and you can. (When the time comes, you might be ready and open to consider a grief group with someone who is trained and skilled in helping you get a handle on things and your feelings. I did after about 6 months, and it was very helpful in sorting things out.) When moments of grief overwhelm you, let it come, then let it go. Watch out for the "landmines," those things that trigger grief. For me it was the drawers that contained her "stuff." When I had to dig into them for one reason or another, I learned to get in, get it and get out as fast as I could, otherwise I couldn't finish and would have to come back later and try again. You'll also probably find yourself doing things that are silly when you allow yourself to think about it, but you do them anyway. I remember my wife's hair brush. It sat on the counter beside the sink for weeks, untouched. Then for weeks I would pick it up, clean under and around it and then set it back down in exactly the same place. It was several months before the day when I started to put it back down, then instead opened a drawer and dropped it in. I knew it was silly, but I couldn't bring myself to put it away before that.
-Get a physical soon, and then have a check up again in about six months and probably again in a year. Be honest and open with your doctor about all that is going on with you, including in your head. Be aware of depression, and let the doctor help you if it's appropriate.
-Even though it gets better, it never goes away completely, and frankly you wouldn't want it to. The price for that is way too high.