kp3004x4

Regular mig would work fine,or if you have a tig. Both probably would need to be on middle to low settings to ensure no warpage or burn through but all metals are different ,I usually take a small test piece and ensure my voltage and speed are enough then try welding.

Ok,I don't know anything about Amazon stuff but,I'd go with something like thishttps://www.mcmaster.com/products/steel-structural-tubing/shape~round-tube the picture is from Amazon but I have bought frame repair tubes from McMaster what ever it really would need to be structural tubing you won't regret it later it's cost a bit more but she'll do. There are other companies that sell structural tubing, sorry for late reply been having family sickness.

First try to find out where switch is located then CHK for different resistance on it with and without switch on. 

Let me know what you need and I'll try to help.