It took me like a week to even figure mods out lol, theres SOOOOO many god damn things you have to do and if you mess up ONE little thing, the whole .jar is shot and you have to start over, so literally every step i take i have to backup that .jar file lol.
Getting mods to work on servers is equally as fun with a different .jar file.
Right now most mods aren't worth using until bukkit is finished/ready along with some minecraft updates coming out soon.
SDK's gun mod is freaking EPIC though lol... nothing like walking up to a zombie and 1 shotting it with the shotgun.
You can even customize the damage and other related data in the mod files too. If you ever get it working, up the timer on the nuke and make the damage something obscene lol... it's hilarious the size of the crater it leaves in the map, straight down to bedrock LOL.
I loves me some minecraft D: