Advancing your timing does help pretty well. Its really simple to do. You can either buy an adjustable timing plate or have your modified. To change the timing with an aftermarket timiing plate all you do is pull your stator cover(the cover on the side of the engine where the chain is) then pull your fly wheel wheel(its one nut) then then take the 3 screws out holding the timing plate, pull the screws holding your pickup and your wires down. Put the new plate in place and re-insert the 3 screws, before you tighten them down though line up where the cases split with the little +4 mark(i think the plate is numbered in increments of 5, so it will be the mark just before +5) then thighten your 3 screws down. Put everything back on the way it came off. Make sure you use some blue lock tight on all your screws and nuts. Should only take about 20 minutes. It could take longer though if its your first time.
As far as the crank you need a 4mil crank(preferably the 4mil long rod), stroker pistons (wiseco 795 series) your cylinders need to be ported for the crank, so you mise well select the port job you want (you can use a spacer plate instead of porting, but I dont recomend that) and you need to either have your stock head cut for the stroker crank or you need to get a cool head with stroker cut domes(I suggest the cool head because then you can change your compression by simply pulling of your head and it uses o-rings instead of gaskets so you dont have to replace them everytime you pull the head(although I would). Also your going to be feeding more motor now so you need to get bigger carbs, and if your not running in mud all the time you mise well get some pod filters to go with them. Another thing you never mentioned is whether you have the stock exhaust or not... If you do you need new pipes and I would suggest that you just start with the basics before going with a stroker. Start with pipes that will really wake up your shee, then when you want some more go with a timing plate, then a cool head with smaller domes to raise your compression, finally I would get it ported and see how you like it. You will be really surprised with hw much that does for your banshee(be sure to re-jet after changing pipes, or getting it ported). Hope that helps