I would say fit side panels first then nosecone then bonnet and scuttle at same time to line things up. The back panel is best done when your car is still up on stands especially if you are doing it in ali, just makes life easier with it at a decent height.

Try not to store your fibreglass panels in such a way that they will distort as they may stay that shape, it is possible to get them back into shape but it can be awkward.

Also don't fix grp down if it's under tension as it will crack during use.

Oh and don't be scared to cut it, apart from the evil dust and stink it cuts easily with a thin disc..use blunt drill bits to drill holes and always use masking tape on the gel coat face as this cuts down the risk of the gel coat chipping.