I'll chime in if you are still paying attention...
Definitely follow Coco's 4-step program.
Going in, my experience level was similar to yours. Except maybe slightly more because I also dabble in hobby electronics/robotics/Arduino type stuff so I knew my way around a soldering iron and was comfortable following build instructions and schematics. My first amp build was a Trinity TC15. I made one minor mistake wiring-up the Contour control, other than that it was smooth sailing... I took my time and it came out great! The great assembly guide was a huge plus and I could not have done it without that for sure.
Also, make sure you have a really good adjustable soldering iron! Something at least like this...
https://www.diyrecordingequipment.com/p ... ng-station or a similar Hakko or BBQ, but for $40 it will be very hard to beat that one I linked.
Now, I am oh a dozen or more amp builds in and just finished my third Trinity kit (OSD and Plexi 6V6.) hint: DON'T start with the ODS as your first build!!! That was easily the 2nd most complicated build I've ever done and lead-dress while always important is EXTREMELY important in this one.
So, if you really really want an 18-watter I think you can do it if you are detail-oriented, take your time and if you are not sure, stop and ask here before moving on. If you are feeling hesitant, start with a smaller kit like one coco suggested.
It is VERY rewarding and VERY addicting! With the DIY spirit I have an amp room full of wonderful amps that would have cost me north of $200,000 if I had purchased the "real deal."
Have fun and be safe!