M17X R1 Help (got a used one and have some questions)

#1
So, I lucked up and got a M17x for DIRT cheap from a local seller. I need help with a few items

1. It only works plugged in (knew this before I bought it). Where is the best place to get a replacement battery and how much would I be looking at? I have checked all around and I can only find replacements for the newer models, not the R1... Any advice here would be greatly appreciated.

2. It has 4GB of ram. I see from the manual it can hold up to 8GB. Dell only sells the 4GB sticks individually, not in a pair and they're expensive. But I'm curious if I ordered two sticks would they work together, I normally only buy ram together and not separate like that.

3. I know in the newer models like my 15 R2 the GPU and other parts can't really be upgraded, but I had heard in these older/bigger models you can. I'm curious what the motherboard can actually hold and BIOS actually recognize. It would be pretty cool to be able to make it decently powerful, if not oh well I'll do some minor upgrades (like getting it to 8GB of ram , instead of the 4GB it's at, and installing a new HDD)...Just curious what CPU and GPUs I could do, what the costs would be, and if it'd be more difficult than my desktop experiences or not. So, what processors and GPUs can the motherboard support? I have the MX17 R1 with the dual core processor.

Any tips or suggestions? I'm already in the process of updating all of the drivers. It was Windows Vista Ultimate on it. I plan to get a Windows 10 key and install it, after I upgrade the HDD. It has a 300GB HDD, I plan to add a new SSD or at least a second HDD with more space.