Compatible Hardware for Lenovo T61

I have a Lenovo T61 and I'm in a low budget planning on buying this SSD: (Just showing amazon for demonstrative purposes, since I'll order them directly from the manufacturer)

https://www.amazon.com/Kingspec-SATAIII-SMI2246XT-controller-ACSC2M064S25/dp/B00Z6THYYU/ref=pd_cp_147_1?ie=UTF8&psc=1&refRID=CR5KF802YZJ65FAGJ5K8

And I was planning on upgrading to 8gb 800mhz Ram. I am not so sure if the T61 supports 800mhz Ram. And after seeing the price, I plan just to upgrade it to 4gb 800mhz ram. It has 3gb 667mhz ram (1gb + 2gb)

What would you recommend? I can buy two 2gb 800mhz Ram, or one 4gb 800mhz Ram but then I would have to leave the 2gb 667mhz ram the computer has installed. If I do this, I'll have an opportunity to buy the next 4gb 800mhz ram in the future... but I'm not sure if it'd be compatible with the 667mhz?

So these are my options:
https://www.amazon.com/Komputerbay-DDR2-SODIMM-800Mhz-6400/dp/B003O9OFE6/ref=sr_1_7?ie=UTF8&qid=1468958972&sr=8-7&keywords=laptop+ddr2+ram+8gb+800mhz

https://www.amazon.com/Studio-Notebook-SO-DIMM-NON-ECC-800MHz/dp/B00VO5R832/ref=sr_1_19?ie=UTF8&qid=1468959030&sr=8-19&keywords=laptop+ddr2+ram+8gb+800mhz

https://www.amazon.com/Memory-Inspiron-Pentium-Dual-Core-Arch/dp/B009KVN21Y/ref=sr_1_40?ie=UTF8&qid=1468959076&sr=8-40&keywords=laptop+ddr2+ram+8gb+800mhz

https://www.amazon.com/GB-SNPTX760CK2-A7548317-Certified-Unbuffered/dp/B00SW54KJC/ref=sr_1_44?ie=UTF8&qid=1468959076&sr=8-44&keywords=laptop+ddr2+ram+8gb+800mhz

Also in the manufacturer's page, it says "PC2-5300" so not sure if it'd be compatible with all of the above:

"PC2-5300 Non-Parity (NP) Double Data Rate Two (DDR2) Technology
The use of 667 MHz SO DIMM memory is recommended for this system.
Recommended for memory expansion are 512 MB, 1 GB, and 2 GB PC2-5300 DDR2 SDRAM 667 MHz SO DIMM"

But I understand since they didn't have 4gb 800mhz ram memories at that time. And I already installed the Middleton Bios Update, so it would be able to accept 4gb and the SATA III will work at full speed as intended.

And also the Battery life has already ended. So I was thinking I could buy one battery like this:

https://www.amazon.com/gp/offer-listing/B005IF78MK/ref=dp_olp_new?ie=UTF8&condition=new

I would really like to hear your comments, since I need this computer to communicate with my family while I'm abroad. I'll be abroad for 4 years.