How hard would it be to build a hk93 clone from a complete parts set and a vector reciever? I have never attemtped something like this.  

Since no one else is going to respond I will. In order to put an HK together requires some knowledge the average builder may not have. Part count compliance is one item. You will not be able to just buy a HK 33 kit and assemble it with a Vector receiver unless you have no more than 10 imported parts[USC title 18 sec 922r]. Plus I'm not 100% sure but in assembling a weapon from a kit may require an ATF form [1?] since you would essentially be manufacturing a new firearm.
You will need a press to assemble the barrel/trunnion assembly to the receiver. You would need access to/experience with some welding equipment to set the charging/cocking tube into the reciever and finish up  the receiver assembly. It's not that this can't be done by the average person, but it may take some trial and error. It is usually left up to someone who has done this kinda thing before and [most importantly] stand by their work.
The more obvious choices would be ORF, IGF and Vector arms. They stand behind their work and have a proven history of quality and commitment.
If you want an already assembled clone 99/33 or 33k check with Jayson @ IGF [Investmentgradefirearms.com]I think he still has some available.  This would be the easier way to go.
YMMV

Thank you,I was wondering if anyone was going to reply. I may buy a vector and a parts kit for spare  parts I don't like the flat navy lower they are selling a the v-93

G3 build
Gives you an idea