My local Honda dealer stocks the new fork seals for that bike. $7.82 ea. You can order from them. Or, just run down to your dealer and pick them up.
http://www.sportlandmotorsports.com/fiche_section_detail.asp?section=2448228&category=Motorcycles&make=Honda&year=1972&fveh=131021
Wife and I just got vinyl, foam and thread from Joanne fabrics and make a seat cover for about $125.00
No, that battery wont work w stock charging system. (seen to many lifepo batteries melt and explode on this forum over the years) AGM or lead acid battery will work all lot cheaper.
Use a dowel and tap the sprocket gently from right side.
Front rim looks great! You will need to balance them also. I dont see any cracks, but, Do you know the age of those tires...safest to assume its time to replace. That rubber is the only thing between your ass and the road. Personally, I like new wheel bearings too. And they are pretty inexpensive.
Turn the chrome spanner nut off key switch. 5ivemotos right. Spray w penetrant and tap it off. You can get a new one on ebay for about $12-15, shipped.