So on a scale of 1 to 10, how hard is it to rebuild(replace gears, seals)an Imco SC upper and lower? I have a pair that will be needing gears in both uppers and I am changing gears in the lowers to a different ratio. Looking to save some money but also educate myself.

Its the same as doing an XR. You need several specialty tools.

You will need to buy the manuals, tools, and I would highly suggest a drive work stand. All in, you are probably looking at $1600 for all the tools and stand. So long as you can follow directions and are patient, you can build your own drives.

I recently upgraded my upper bravo 1 to XR with a 1:35, I was going to reuse the lower 1:65 until I eventually upgrade to an imco with same gear.But for now would the final gear ratio be ?

All XR upper gears are the same. The ratio in an XR is changed with the gears in the lower.
It may still come out as 1.5 as JT said(I don't know and he knows a ton more than me about XR's) but there is really no such thing as a 1.35 upper XR.