I have had my hands on three HP laptops over the last two years and can`t agree that the HP website is poor on tech support. Needs a bit of hunting through the masses of information perhaps!
Laptops are notoriously difficult to upgrade other than basic memory, HDD etc because every manufacturer uses bespoke components unlike a desktop/tower where you can mix and match fairly easily. Consequently the costs of upgrades are prohibitive and batteries alone cost around £100 for a lot of models. That aside, there are specialist laptop repairers who can get the parts but they know how to charge as well.
My laptop was a Compaq Evo 1015V and about 3 years old and cost £800 new. An excellent reliable machine. I had spent £120 on a new battery 6 months ago and then an inverter failure rendered it useless. Estimate for repair about £150. If the two decisions had been made at the same time I wouldn`t have repaired it. An upgrade in memory and a bigger 60Gb HDD would cost about £140 to DIY - so I could spend almost the cost of a new laptop of similar spec.
Give us the make and model and let us know what you want to achieve in the upgrade including what you want to use it for. Might have some suggestions.